On my DAP1360, which I'm operating in AP mode, Wireless Access Settings gives the following three options:
Turn MAC Filtering OFF
Turn MAC Filtering ON and ALLOW computers listed to access the network
Turn MAC Filtering ON and DENY computers listed to access the network
I'm unable to enter any MAC addresses (i.e, the fields are greyed out) until the second or third option has been selected. So you can either ALLOW a number of computers access, or DENY a number of computers access, but not both. You have to make a choice. Although I haven't used this feature on my DAP-1360, this is exactly the way it works on the DIR-655, and I suspect most, if not all, D-Link products.
Although I haven't tested this, I agree with FuzzyNutz, in that this feature probably doesn't work in Repeater mode, and is certainly not necessary, as the DAP should simply mirror the router settings.
Larry ....