diff --git a/src/SQLInsight.Core/Data/Indexes.cs b/src/SQLInsight.Core/Data/Indexes.cs
index 98850d6..9123ef6 100644
--- a/src/SQLInsight.Core/Data/Indexes.cs
+++ b/src/SQLInsight.Core/Data/Indexes.cs
@@ -70,7 +70,8 @@ public sealed record IndexInfo
     /// <summary>Since when SQLInsight has followed the usage (the restart before the first collection).</summary>
     public DateTimeOffset? TrackedSince { get; init; }
 
-    public string Key => $"{Schema}001f{Table}001f{IndexId}";
+    /// <summary>Identifies the index within its database across collections (unit separator between the parts).</summary>
+    public string Key => $"{Schema}\u001f{Table}\u001f{IndexId}";
 
     public long Reads => UserSeeks + UserScans + UserLookups;
     public double SizeMb => UsedPages * 8.0 / 1024;
@@ -134,8 +135,10 @@ public static class IndexUsageTracking
             Indexes = d.Indexes.Select(i =>
             {
                 before.TryGetValue(d.Name + "\u001f" + i.Key, out var was);
-                var reads = restarted || was is null ? i.Reads : Math.Max(0, i.Reads - was.Reads);
-                var writes = restarted || was is null ? i.UserUpdates : Math.Max(0, i.UserUpdates - was.UserUpdates);
+                // A counter lower than last time was reset without a restart (database taken offline or closed by
+                // AUTO_CLOSE, index rebuilt on 2012/2014): what it holds now is all new.
+                var reads = restarted || was is null || i.Reads < was.Reads ? i.Reads : i.Reads - was.Reads;
+                var writes = restarted || was is null || i.UserUpdates < was.UserUpdates ? i.UserUpdates : i.UserUpdates - was.UserUpdates;
                 if (reads > 0 || writes > 0)
                 {
                     deltas.Add(new IndexUsageDelta(d.Name, i.Schema, i.Table, i.Name, reads, writes));
diff --git a/tests/SQLInsight.Core.Tests/IndexUsageTests.cs b/tests/SQLInsight.Core.Tests/IndexUsageTests.cs
index 5d2f3ac..ba5813c 100644
--- a/tests/SQLInsight.Core.Tests/IndexUsageTests.cs
+++ b/tests/SQLInsight.Core.Tests/IndexUsageTests.cs
@@ -30,4 +30,16 @@ public class IndexUsageTests
         Assert.Equal((5L, 200L), (delta.Reads, delta.Writes));
         Assert.Equal((2L, 50L), (afterRestart.UsageDeltas[0].Reads, afterRestart.UsageDeltas[0].Writes)); // counters started over
     }
+
+    [Fact]
+    public void A_counter_reset_without_a_restart_counts_what_the_counter_holds_now()
+    {
+        // The database was taken offline (or closed by AUTO_CLOSE) between the collections: same start time, lower counters.
+        var first = IndexUsageTracking.Advance(null, Snapshot(Start, new DateTimeOffset(Start.AddDays(1)), 100, 1000));
+        var second = IndexUsageTracking.Advance(first, Snapshot(Start, new DateTimeOffset(Start.AddDays(2)), 7, 40));
+
+        var delta = Assert.Single(second.UsageDeltas);
+        Assert.Equal((7L, 40L), (delta.Reads, delta.Writes));
+        Assert.Equal((107L, 1040L), (second.Databases[0].Indexes[0].TrackedReads, second.Databases[0].Indexes[0].TrackedWrites));
+    }
 }