The quick and easy way to solve this issue is to create a larger pool of IP ranges - see the example below:
However, if this device is being used in a hotel and guests potentially have access to the same network as your servers / staff PC’s, etc then perhaps create a VLAN for the guests to use, with a larger pool of IP addresses. The example below shows a couple of example VLAN’s, with separate IP ranges. (Network -> LAN Network Settings).
Then configure the port(s) - Network -> LAN Port Settings - you may also need to configure any switches, Access Points, etc with the appropriate VLAN’s.
You would probably want to make sure inter-VLAN routing is off, to prevent guess users from accessing your “office” based network.
Hope this helps,