Due to recent discoveries¹ in Any% , new timing rules are in effect as of July 26, 2020. ( ¹ https://www.speedrun.com/gtavcs/thread/deoe1 )

Start of timing for all categories:
The first frame after confirming a new game.

End of timing for Any%:
The first visible frame of the End Credits

Current runs are being retimed as of right now.

Starting August 1, 2020 newly submitted runs with videos cut too short (whose time cannot be determined according to the timing new rules) will be rejected.