I just answered in your other post as being zero to several decimals. The expert shooters are all saying there's no way to do this with the precision necessary, the error margin is up to 3 inches with this gun, and the head keeps moving, and there's wind. I can't contradict that, no white hat would script it this way unless they had more control than we can imagine. Clever magicians could script something similar but there are too many risks for things to go wrong in the actual circumstances that transpired, and there would be tells that indicate where they had a secret hand in things. Here no tells are aligning into one explanation. Except:

The only person who could "set this up" to achieve objectives is God. The clearest answer is that everything points to him as having chosen Trump to get grazed but neither missed nor killed. He orchestrated things so that no human or agency could take credit as having anticipated everything. So that's my stance unless anyone can show anything different. Every theory trying to explain this as humanly anticipated has holes in it.