Most loading bars I know nowadays just are timed and have no connection to the thing loading.
So you just double the time it takes to get to the next percentage.
0.1 second for the first
2.4 seconds for the 9 to 10%
It will take hours to get from 99 to 100.
But it just completes when it is actually done.
I just let chatgpt rerun the numbers and it says it will take 300 billion years to get from 99 to 100.
Lol