What is the ruling on swallowing saliva after the Adhan out of forgetfulness while fasting, and is making up for the missed days obligatory despite not knowing their number?

If a fasting person hears the Fajr Adhan while food is in their mouth, they must spit it out. If they swallow it, their fast is invalidated. As for someone who did this out of ignorance, the فقهاء (jurists) differ on whether they must make up the fast or not. The more cautious approach for them is to make it up. If they do not know the number of days they missed, they should investigate and make up the number of days they most likely missed.