I have the same model.
I managed to set some IP addresses for some systems which I wanted fixed, linked to MACs.
Contrary to my expections, these addresses did not get applied when I used DHCP with those systems.
If you have the same software version, it is terrible (in my opinion).
Initially, I had to make some changes, which were for other features I wanted, by adjusting a configuration file (save coniguration, edit the saved, text, file, restore from it, and reboot)