there seems to be some weirdness going on, some times being with miliseconds and some without, if you're having problems with retiming runs, I recommend downloading Tampermonkey (Chrome add-on) and then this: https://greasyfork.org/scripts/383980-youtube-speedrun-timer/code/YouTube%20Speedrun%20Timer.user.js

if you want I can also help, I'm a mod of a few short games so I'm experienced retiming runs to frames