Weekly days off is non-working day which can be predefined on user's profile by following the steps below:-

–  Login as Administrator.
–  Click on Administration Icon
–  Click Users on the left pane.
–  Double click on the employee's account.
–  Click Advanced tab.
–  Click Add under Other section to add Weekly days off.

Weekly days off should not count as time off. Check to see if the weekly day off setting was changed after the time off was booked. 

 
If this is the case, if you reopen and resubmit the booking, it should no longer display as time off on the weekly day off.