Server RPT ‐ What and Where
It's ArmA's Logfile and stands for "report"
Arma generates a .rpt log file each time it's run, which contains a lot of information like the loaded mods, or any errors that appear, this log file can be very useful for troubleshooting problems.
https://community.bistudio.com/wiki/Crash_Files
Pretty simple - open faster, select your server Profile, Select the Profile TAB and in the bottom right, where you can read the name of your profile, right click.
This will open the "Faster-ServerProfile"s "Arma Profile" folder.
In here, you want to search for your most recent .rpt File. The latest .rpt file in there is your server log.
make sure to not run your server with -noLogs