diff --git a/web/src/components/ProductDetail.tsx b/web/src/components/ProductDetail.tsx
index a9a48ab..60b269c 100644
--- a/web/src/components/ProductDetail.tsx
+++ b/web/src/components/ProductDetail.tsx
@@ -294,7 +294,7 @@ export function ProductDetail({
                   {cfg?.unit}). Re-audit to update.
                 </div>
               )}
-              {item.containerWeight != null && (
+              {item.containerWeight != null && last && (
                 <div
                   style={{
                     fontSize: 11,
diff --git a/web/src/types.ts b/web/src/types.ts
index 734968a..938eb88 100644
--- a/web/src/types.ts
+++ b/web/src/types.ts
@@ -211,16 +211,15 @@ export const helpers = {
       return p.countLastAudit ?? p.countOriginal;
     }
     const last = this.lastAudit(p);
-    const baseDate = last ? last.date : p.purchaseDate;
-    const baseValue = last ? last.value : p.weight;
+    if (!last) return p.weight;
     const daysSinceBase = Math.max(
       0,
-      Math.floor((+new Date(today) - +new Date(baseDate)) / 86_400_000),
+      Math.floor((+new Date(today) - +new Date(last.date)) / 86_400_000),
     );
     const expectedLifespan =
       p.type === "Flower" ? 35 : p.type === "Concentrate" ? 40 : 90;
     const dailyBurn = p.weight / expectedLifespan;
-    return Math.max(0, baseValue - dailyBurn * daysSinceBase);
+    return Math.max(0, last.value - dailyBurn * daysSinceBase);
   },
   pctRemaining(p: Item, today = TODAY_STR): number {
     if (p.kind === "discrete") {