Clarifying the partial-Day deduction rule

Q. I have a question about the partial-day deduction rule. I don’t understand how we can deduct from salaried employees’ paid-leave bank when they are gone for an hour or two during the day since we don’t pay them anything extra when they work 50 hours in a week. For example, if an employee works 10-hour days on a regular basis, is it OK to charge her vacation time when she leaves an hour or two early? —J.H., Minnesota