One kid of the goats. "One hairy one ( שָׂעִיר) of the she goats ( עֵן)." See on Numbers 7:16. This was probably offered first in order, according to the usual analogy of such sacrifices (Exodus 29:10-14).
There is no authority for supposing that this sin offering superseded the one mentioned in Numbers 15:24 sq. This was essentially part of the customary routine of sacrifice; that was essentially occasional, and proper to some unforeseen contingency.
It is likely enough that the national conscience would in fact content itself with the first, but it does not in the least follow that such was the intention of the legislator.