PokeDad: If you'll check past prerelease attendance threads, you'll notice no one has ever counted their booster drafts in reporting prerelease numbers. NEVER. PTOs know what numbers to report. We report on these threads what we report to PUI -- UNIQUE players from BOTH the sealed pack and theme deck events.
And when you report for City Championships, Gyms, and Regionals, you report just the tournament numbers. You don't include the number for drafts or any other side event. Occasionally, someone will report those numbers, and that's okay -- but they're always reported separately and never counted as part of the event's tournament attendance/participation numbers. It's been like this forever and it works.
I realize that this is your first attendance thread. In the future, I recommend that instead of trying to figure out numbers yourself, just start an attendance thread and let the PTOs report the numbers themselves. They'll report correctly.