diff --git a/crates/blackbeard-api/src/ingest.rs b/crates/blackbeard-api/src/ingest.rs
index 7a5bc45..0c7680e 100644
--- a/crates/blackbeard-api/src/ingest.rs
+++ b/crates/blackbeard-api/src/ingest.rs
@@ -189,7 +189,13 @@ pub async fn warm_start(chain: &Arc<ChainRuntime>, store: &Store, ticker_blocks:
                 // interval.
                 inner.window.push(block, false);
             }
-            tracing::info!(chain = %id, blocks = count, "warm start: window restored");
+            // `held` as well as `blocks`: the two must agree, and when they did
+            // not, every share on the site was computed over the difference
+            // without anything saying so. See #13.
+            tracing::info!(
+                chain = %id, blocks = count, held = inner.window.len(),
+                "warm start: window restored"
+            );
         }
         Err(e) => tracing::warn!(chain = %id, error = %e, "warm start: no window restored"),
     }
diff --git a/crates/blackbeard-api/src/state.rs b/crates/blackbeard-api/src/state.rs
index 13be1b4..0b42525 100644
--- a/crates/blackbeard-api/src/state.rs
+++ b/crates/blackbeard-api/src/state.rs
@@ -364,6 +364,13 @@ impl ChainRuntime {
     pub fn recompute_leaderboard(&self, window: Window) -> (Vec<LeaderboardRow>, bool) {
         let mut inner = self.write();
         let (tallies, total) = inner.window.tally(window.blocks() as usize);
+        // The denominator of every share on the board, against what the window
+        // actually holds. See #13: these disagreed with the warm-start count by
+        // two orders of magnitude and nothing on the page said so.
+        tracing::debug!(
+            window = ?window, asked = window.blocks(), held = inner.window.len(), tallied = total,
+            "leaderboard recomputed"
+        );
         // The window's own duration, by the chain's clock. Every per-miner
         // hashrate is its summed work over this — not its share of the current
         // network, which credits a miner that won while the network was small
diff --git a/crates/blackbeard-core/src/window.rs b/crates/blackbeard-core/src/window.rs
index ce2e67e..c32e453 100644
--- a/crates/blackbeard-core/src/window.rs
+++ b/crates/blackbeard-core/src/window.rs
@@ -338,6 +338,40 @@ mod tests {
         }
     }
 
+    /// The window keeps everything it is given up to capacity, and the tally
+    /// reads the newest `n` of them.
+    ///
+    /// Filed as #13: warm start reported restoring 19,910 blocks and the board
+    /// it served divided by 1,065. One of the two had to be wrong, and this
+    /// pins the half that lives in this crate — so an investigation upstream of
+    /// it does not have to re-establish that a deque holds what was pushed.
+    #[test]
+    fn a_restored_window_tallies_the_whole_requested_span() {
+        let mut w = RollingWindow::new(100_800);
+        for h in 1..=19_910u64 {
+            w.push(
+                Observed {
+                    height: h,
+                    miner: MinerId(format!("m{}", h % 7)),
+                    observed_at: Utc::now(),
+                    authored_at: None,
+                    difficulty: None,
+                },
+                false,
+            );
+        }
+        assert_eq!(w.len(), 19_910);
+
+        let (_, total) = w.tally(3_600);
+        assert_eq!(total, 3_600, "a full window must tally the whole window");
+
+        let (_, total) = w.tally(100_800);
+        assert_eq!(
+            total, 19_910,
+            "asking for more than is held tallies what is held"
+        );
+    }
+
     #[test]
     fn the_window_drops_the_oldest_block_when_full() {
         let mut w = RollingWindow::new(3);