Missing "IP Range" into User Group definitions

In some scenario, e.g. when the dhcp is not router, but other server in lan,
is particulary tedious insert only one IP per row to define user group membership.

From drop-down menu, besides “IP address” and “Subnet”, is necessary the “IP Range” feature.

In other posts, you have suggested to use “Subnet” to specify a range to put in “staff” group, but I don’t understand how.

For example, if I have:
Peplink Balance 210
Router ip

from to must be “Manager”
from to must be “Staff”,
from to must be “Manager”
and the others “Guest”, how do I do? Instead of put every single ip on every single rule?

Thanks in advance.