If you're trying to display the number of days available, try:
round({table.vacationhours} / 8,0)
Then to correct the display to eliminate decimals, right click the field and select format field->Number and select the -1123 format.
If you already had the field worked out to divide by 8, you can just right click it select format field->Number->Cistomize and set the rounding to your preference.
-k
Most companies only allow for days which have been entirely earned, in that case it would be: