Very long timestamp for a backup file created via a Maintenance Plan

I have been using Maintenance Plans to back up my databases. It works well enough for me but I am curious to know why the .bak have a very long date/time suffix. Here is an example: MyDatabase_backup_2022_10_27_213008_2710399.bak I can see the yyyy_MM_dd_hhmmss format but what about the rest (2710399), microseconds...? Thanks,