It will make not a jot of difference in the grand scheme of things.
Anything above 10 days of progesterone is adequate for endometrial protection.
If you are still having regular periods and happen to be that person with a regular 28 day cycle that is in every textbook but no clinician has ever actually met, and you are expecting your natural period to coincide with stopping the progesterone, then I would stop on the same day you planned to, otherwise your period and the withdrawal bleed could end up out of sync.