I'm speedrunning a niche Minecraft% where runs are currently 30 seconds or shorter. Is it correct to use real life time (using recorded frames as reference) or the in-game time when measuring runs? Recently a run was faster in real time but slower in in-game time than another player's semi-laggy run.

If in-game time is the correct measurement to use, is the an IGT for 1.13+? Thanks.