Charles Ellicott Commentary Numbers 31:32

"Now the prey, over and above the booty which the men of war took, was six hundred thousand and seventy thousand and five thousand sheep," — Numbers 31:32 (ASV)

And the booty, being the rest of the prey ... — The reference may be to the residue of the captives after the slaughter of all the males and of a large number of the women, and to the cattle which were brought to the camp, some, perhaps, having been lost or slaughtered for food; or it may be to the booty which had been taken in captives and animals, as distinguished from the gold and silver, etc.