What do you do if you doubt the number of prostrations? Thank you.

If the doubt occurs after finishing the prayer, it should be disregarded unless there is certainty of a deficiency or an excess. However, if the doubt occurs during the prayer, one should base it on the lesser amount, as the Prophet, peace and blessings be upon him, said: "If one of you doubts in his prayer and does not know how many rak'ahs he has prayed, three or four, he should cast away the doubt and build upon what he is certain of, then prostrate twice before giving the salutation." This ruling is specific to one who does not frequently experience doubts; otherwise, they should be disregarded.