Wa alaykum salam wa rahmatuLlahi wa barakatuHu,
According to the relied-upon opinion in the Shafi’i Madhhab, khulu’ is divorce. Consequently, when it is given, the number (i.e. three) of divorces that one has is reduced. Accordingly, if by giving it one expended all three, then the marriage would only be valid after the woman married another man, had intercourse with him, and then a divorce took place between them followed by her completing her waiting period. There is another opinion related from Imam Shafi’i and others that considers khulu’ to rather be an annulment and not a divorce. And according to this view, khulu’ does not reduce the number. (Rawdat al-Talibin 7/375)
And Allah knows best.
Answered by: Shaykh Yaqub Abdurrahman