New Firmware Fritzbox and Wireguard

sorry for my bad english, i use google translator!
The new laboratory firmware of the Fritzbox 7590 finally allows Wireguard Server and I would like to create a profile for my SPITZ (for Camping), the Fritzbox asks for the subnet when creating it, what should I enter here? I’m sorry, so far I’ve used a CRETA as Wireguard server, I didn’t have to enter anything like that and it worked immediately! But I would like to remove the CRETA from the Fritzbox and do everything via the Fritzbox!

you can use,
This is what we used by default.

great thank you so much