Still unsure if the in-game timer is accurate or reliable, so the default time for the leaderboard will still be real-time.

however, we understand that the final time is converted like so:

Example: 2:19:05 = 2195 seconds = 45 minutes 41 seconds

The rightmost 2 digits are just a 1-9 timer, every time it ticks to 10, it adds to the "2:19" digits, and basically just counts the seconds up. You can then easily translate that to a full number of seconds, in this case, 2195, and convert it.

Any time converter will do, here's one I used: https://www.tools4noobs.com/online_tools/seconds_to_hh_mm_ss/