Hello @bturner
Have a look at Meraki Go - Local Network Addressing - Cisco Meraki
If you want change the scope, set a new Subnet Mask. 24 (default setting) gives you 253 ip-adresses, 25 would give you 125 and 30 only 1 ip-adress.
You could also set a list of Reserved IP-Adresses, that would stop the GX50 from deploying them to clients:
Cheers