Could someone please clarify this problem to me?

Given a string S and a string T, count the number of distinct

subsequences of T in S.A subsequence of a string is a new string which is formed from the

original string by deleting some (can be none) of the characters

without disturbing the relative positions of the remaining characters.

(ie, "ACE" is a subsequence of "ABCDE" while "AEC" is not).Here is an example: S = "rabbbit", T = "rabbit" count = 3

If I understood correctly, we need to find all distinct subsequences of T and see how many, if any appear in s. How does that equal to 3 in the given example?