Voluntary Leave without pay

We have a salaried employee who has taken leave without pay. I set up the LWOP Category as a wages category and entered a minus amount to deduct this leave off his pay. All seemed good until I checked Payroll Reporting and found that it had included the amount of the minus of the LWOP into the YTD of the employee in Payroll Reporting. What have I done wrong? It should not be included in the employees YTD with Payroll Reporting! I would appreciate some advice regarding this matter