I compared it to the Trump inauguration on video. The guns were within earshot of the swearing in ceremony and started when Trump finished his pledge. There were 21 shots at 3 second intervals for Trump. Hard to compare Biden as they were not in earshot and clearly not at the same location, maybe not even the same day. However many shots there were, they were all 10 seconds apart. I looked at a couple of versions and counted more than 3 shots but the 10 second intervals were consistent.

Salute from the Cemetery!