The daily limit often seems to fail in detecting the start and then the end of the day.
As example - today I started unlocking my computer at 9:30, but according to workrave I had only 5h left to work.

Why does it not detect correctly, when inactivity afte resetting at 4:00am to see, when the work day starts?

Does you computer sleep or hibernate?

Workrave should reset the timers at 4:00 by default, or when it returns from hibernate/sleep if the computer was hibernated at 4:00.

Do you at 9:30 get the same timer values as when you stopped working the day before? Or did you computer somehow generate new activity after 4:00?