I set the daily limit to 0, the weekly limit to 2520 which should equal 7x 6h, and the reset day to 1 which should be monday.
Now when I login, it just displays me that I only have about 5 hours left.
How could that happen?

Hello Krangh, sorry to hear your having troubles. Unfortunately, I no longer have access to a Rust server to reproduce issues or test bug fixes. Did you use the workingman.setweekstartday command to set the day? I would try experimenting with this command and/or the config file and reloading the plugin. I haven't had any issues with this feature in the past and had no previous issues regarding this reported to me. Hopefully you can get it worked out. Good luck!