Yearly Vacation Accrual based on Anniversary Date (2.19.2)

Reading the documentation and just don't get it - how would you setup a Time Off code for a client who gives vacation accruals at the start of each anniversary year?  I have the Anniversary check box checked in Setup, but can't check the Periodic Accrual (only) as the accrual basis.  Setting up a code as Fixed puts the Hours as the LIMIT bit gives me nothing for Available.

Help!