وَالضَّرْبُ الثَّانِي: مَا يَثْبُتُ فِي الذِّمَّةِ،
Translation: The second category consists of fasts established as a liability.
A fast “established as a liability” is still owed, but today’s date by itself is not assigned to that duty.
When making up a missed Ramadan fast, the current date does not automatically identify which obligation is being fulfilled. The intention must identify the obligation, and its timing is more restrictive.