General vacancy reduces revenue by the amount specified.
Make sure you have entered all of your tenants. Check the property size. If there are tenants with expiring leases, reimbursements will not be paid during the months in which the space is vacant. Check the Inflation Method and the Reimbursement Method on the Property Inflation window. If these do not match, it is possible that reimbursements based on a calendar period will not match fiscally inflating expenses.