What does manual time offset do? And where does Series guide pull the airing time from?

Help and Bugs
1

The gen:LOCK series airs every Saturday at 10AM CST. But I got a notification 4 hours before itself (even though my notification is set for 10 minutes before) and the show shows as already released.
Is the airing time wrong due to TVdb? Can this be fixed by using the manual time offset? Or should I report in the tvdb forums

2

See https://seriesgui.de/help#airtimes

The time offset can be used to adjust the release times to your preference, but it will affect all shows.