How do they take your bah?

k, so im moving on post first time. im done with all paper work. i know how it all goes, what it covers and all. only question i forgot to ask them was..... do they take the whole bah at once? or do the split it in payments. like say ur pay was 950. would they take it all in one, or would they take 475 on the first and then the second 475 on the fifteenth? just wondering so i know how much my husbands next pay will be. thanks!