I found that monthly balance show me wrong value as soon as I log some hours during weekend.
Any log will make day as "working" and add 8h to my required hours.

i.e. I work 8h Mon-Fri = 40h, Monthly balance: 0h
I log 1h on Sat = 41h, Montly balance: -7h

It would be nice to have either option to choose which days are working days or how many of days we work withing week or simply set hours for whole week.

For me that would be 40h, and any work above that would be overtime.

This feature would be very usefull for any felxible workingtime scheme