diff --git a/frontend/src/capture/capture.types.ts b/frontend/src/capture/capture.types.ts
index db28ce9..755eb6e 100644
--- a/frontend/src/capture/capture.types.ts
+++ b/frontend/src/capture/capture.types.ts
@@ -43,7 +43,7 @@ export interface Mask {
   slabPx: number; // 0 ⇒ approve blocked, user retakes
   bitset: Uint8Array; // source-grid mask, 1 byte/px
   bbox: BBox;
-  slabBounds: ABox; // axis-aligned extent of slab px, for the 80%-fill PNG crop
+  slabBounds: ABox; // axis-aligned extent of slab px; the PNG crop bounds (#99)
 }
 
 export interface PhotoTransform {