四分律行事鈔資持記 2.1147

2.1147

釋中，初科，前示名相。必約受己方得成殘。四下，示藥體。時藥過中吉，隔宿提。非時七日過限，盡形無病緣，皆名殘；同前非時。上引本律。善下，引他部。約受論殘，不取食殘。

In the explanation, the first subsection: the former part shows the terminology. It must be after having received it that it can constitute a leftover. Below, from "Four", it indicates the substance of the medicines. For timely medicine, passing noon incurs a duṣkṛta, and keeping it overnight incurs a pāyattika. For non-timely and seven-day medicines, exceeding their limit, and for lifetime medicine, lacking the condition of illness—these are all called leftovers; they are the same as the improper times above. The above cites this Vinaya. Below, from "Samantapāsādikā", other traditions are cited. Leftovers are judged based on reception, not based on leftovers from eating.