The in-game timer should be used for this game with the milliseconds.

in-game time and milliseconds added

I also think full-runs should be using the in game time of each levels additioned as timing method.

I have a site that lets you addition times with seconds and milliseconds https://datetimecalculator.net/time-calculator

You should try this game

If you’re looking for a more accurate count, a days calculator might help.