Fact is, imo, and imbw, to expect all ear witness are going to recall everything they heard that traumatic night, and to all hear exactly the same is pie in the sky. Each will hear differently. It will depend on each person's hearing, on what they were paying more attention to at a given moment, on whether they were facing left or right or looking out or in, on whether a gust of wind went by and the noise momentarily changed direction, etc. etc. etc.
I don't really understand why it is so significant the number of "shots" each heard either, and much less still if the defence is trying to claim double taps which I would think it would be harder to distinguish one from the other.