Suppose 7 fasts were missed for a qualifying illness, then the person recovered for only 3 days before death and had not performed the make-up. On the principle described, the liability is limited to 3 days, not 7, because that was the available period.
The example assumes those 3 days were usable for qaḍāʾ, with no other excuse. Any estate or bequest consequences require their separate legal conditions.