How could that be possible?
The simple answer is that there are two fewer selling day in August, so the number of vehicles sold is down, but the sales rate is up.
There is also a more complex answer that delves into the segment level adjustments that go into SAAR, but I will spare you this detail.
One more complexity: the government just announced its new SAAR factors, which not everyone plans to use when announcing August. (Edmunds will.) So expect an unusually wide varition in SAARs along with the August numbers.