fix(report): use parts per plate consistently

docs/nest-reports.md

@@ -54,7 +54,9 @@ each plate's part table across pages with the heading row repeated, and notes
 flow as an ordinary paragraph. No row, table or note text is ever dropped or
 truncated to fit a page.
 
-Stock sizes read **width x length** in job units. Plate counts use **Quantity**.
+Stock sizes read **width x length** in job units. Plate tables use **Quantity**
+and **Parts per plate**; the plate quantity multiplies per-plate part counts for
+the totals.
 
 Each part ID is centered on its part's pole of inaccessibility (`PolyLabel`,
 the same method `PlateView`'s `LayoutPart` uses), computed on a