diff --git a/src/Schedule.hs b/src/Schedule.hs
index 84d6879..9a64ebc 100644
--- a/src/Schedule.hs
+++ b/src/Schedule.hs
@@ -56,7 +56,7 @@ scheduleByMedicine pharmacy day medicineName stockLeft rate =
   where
     (Medicine {minStock, content}) = pharmacy ! medicineName
     truncateF = fromInteger . truncate
-    leftInBox = content - (truncateF (content / stockLeft) * stockLeft)
+    leftInBox = stockLeft - (truncateF (stockLeft / content) * content)
 
 typeAndAmount :: Float -> Float -> Float -> (ScheduleType, Float)
 typeAndAmount stockLeft minStock leftInBox =