What is the ruling on one who doubts the number of days they missed fasting in Ramadan due to a legitimate excuse, and these days have accumulated over several years?

Whoever breaks their fast in Ramadan due to a legitimate excuse (such as travel or illness) must make up the days they missed, according to the verse: "But whoever among you is ill or on a journey [during them] - then [he must make up] an equal number of other days." If one is unsure about the number of days, they should fast the greater number as a precaution and to clear their conscience. If one is unsure about the original act of fasting, they must make up the days about which they are uncertain regarding their fasting.