I had about the same count, although a few of those sounded like more than one shot at the same time. Multiples could push the count to 69 or 70 after the recording started. Presumably there was some rapid shooting before that also.
I tried to count the multiples as a single.
It could have been security and the perp firing at the same time. Sometimes standing by a wall could cause an echo effect, so I just erred on the side of one shot.
That could certainly be objected to.
Your comment about other shots prior to the start of the video would seem reasoned.