AP, they correspond to the Primary Mathematics series from Singapore-- so I'm not entirely sure how they would work in conjunction with another math curriculum. If you're using something else, I'd probably have your DD run through the placement test on Singapore's website to see where they think she's at in their sequence.
Then I'd order at that level, and maybe (depending on whether or not she seems to have gaps on that assessment) one down from there. Fortunately, they are quite inexpensive, so little risk.
