diff --git a/solar_relay/web/index.html b/solar_relay/web/index.html
index 096f210..458492a 100644
--- a/solar_relay/web/index.html
+++ b/solar_relay/web/index.html
@@ -30,8 +30,13 @@
     </section>
     <section class="panel">
       <div class="panel-heading"><div><p class="eyebrow">DAILY COVERAGE</p><h2>Five-minute completeness</h2></div><label class="range">History <select id="history"><option value="7">7 days</option><option value="14" selected>14 days</option><option value="30">30 days</option><option value="90">90 days</option></select></label></div>
-      <p class="panel-note">Complete means a valid energy, meter and boiler extraction in that five-minute interval. It does not mean continuous measurement. Recovered cloud history supplies energy only.</p>
-      <div class="table-scroll"><table><thead><tr><th>Day</th><th>Complete intervals</th><th class="source-column">Energy</th><th class="source-column">Meter</th><th class="source-column">Boiler</th><th>Status</th></tr></thead><tbody id="days"><tr><td colspan="6" class="empty">Waiting for the local archive…</td></tr></tbody></table></div>
+      <p class="panel-note">Each count shows five-minute intervals with valid data out of the elapsed intervals for that day. Complete intervals have all three sources. Polling does not guarantee continuous observation. Solar.web recovery fills Energy only.</p>
+      <dl class="coverage-definitions">
+        <div><dt>Energy</dt><dd id="energy-description">Solar production, household consumption and electricity imported from or exported to the grid. Available from live readings or recovered Solar.web history.</dd></div>
+        <div><dt>Meter</dt><dd id="meter-description">Running totals of electricity bought from and sold to the grid. Requires live meter readings; Solar.web history cannot fill these counters.</dd></div>
+        <div><dt>Boiler</dt><dd id="boiler-description">Boiler control output: enabled or disabled. Both states count as valid data. Heating energy is not measured, and Solar.web cannot recover past switch states.</dd></div>
+      </dl>
+      <div class="table-scroll"><table><thead><tr><th scope="col">Day</th><th scope="col">Complete intervals</th><th scope="col" class="source-column" aria-describedby="energy-description">Energy</th><th scope="col" class="source-column" aria-describedby="meter-description">Meter</th><th scope="col" class="source-column" aria-describedby="boiler-description">Boiler</th><th scope="col">Status</th></tr></thead><tbody id="days"><tr><td colspan="6" class="empty">Waiting for the local archive…</td></tr></tbody></table></div>
     </section>
     <section class="panel detail" aria-label="Selected day interval details">
       <div class="panel-heading"><div><p class="eyebrow">FIVE-MINUTE INTERVALS</p><h2 id="selected-date">Select a day</h2></div><div class="legend"><span><i class="complete"></i>Complete</span><span><i class="partial"></i>Partial</span><span><i class="missing"></i>Missing</span><span><i class="future"></i>Upcoming</span></div></div>
diff --git a/solar_relay/web/status.css b/solar_relay/web/status.css
index a008cb2..46915e6 100644
--- a/solar_relay/web/status.css
+++ b/solar_relay/web/status.css
@@ -1,4 +1,6 @@
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+.coverage-definitions{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:20px;margin:0;padding:0 24px 24px}.coverage-definitions dt{font-size:11px;font-weight:650;margin-bottom:6px}.coverage-definitions dd{margin:0;color:var(--muted);font-size:11px;line-height:1.7}
 @media(max-width:900px){.metrics{grid-template-columns:repeat(2,minmax(0,1fr))}.metric{padding:20px}.source-column{display:none}.legend{max-width:215px;gap:10px}.slots{gap:4px}.progress{width:115px}}
+@media(max-width:560px){.coverage-definitions{grid-template-columns:1fr;gap:14px;padding:0 16px 20px}.coverage-definitions dt,.coverage-definitions dd{font-size:10px}}
 @media(max-width:560px){main{padding:0 16px}.masthead{height:82px}.brand{font-size:11px;gap:8px}.sun{font-size:30px}.header-actions{gap:8px}.refresh span{display:none}.refresh{font-size:17px;padding:4px 9px}.badge{font-size:10px;padding:6px 8px}.intro{padding-top:30px}.metrics{gap:10px;margin-bottom:20px}.metric{padding:17px 14px}.metric strong{font-size:26px}.metric strong span{font-size:14px}.metric-label{margin-bottom:14px}.metric small{font-size:9px}.panel-heading{padding:20px 16px 0;align-items:flex-start}h2{font-size:16px}.panel-note{padding:0 16px;font-size:10px}th,td{padding-left:11px;padding-right:11px}th:first-child,td:first-child{padding-left:16px}.progress{width:88px}.range{flex-direction:column;align-items:flex-end;gap:5px}.legend{font-size:9px;gap:7px;max-width:150px}.slots{padding:0 16px;gap:3px}.hour{min-width:10px;grid-template-rows:16px repeat(12,5px);gap:3px}.hour-label{font-size:8px}.gap-summary{padding:16px;font-size:10px}.day-select{font-size:11px}footer{font-size:9px;flex-wrap:wrap}.detail .panel-heading{gap:8px}}