I have used 192.168.1.0 as opposed to 192.168.192.0 as per the example to align with my existing network.
Unfortunately when attempting to complete the UI step to delete all existing managed routes and add my own managed route when entering “192.168.1.0/24” as the Destination under “Add Route”, although it adds the route successfully it appears as "192.168.0.0/23 (LAN).
It’s working correctly because that’s just how the math works out when calculating network sizes. With a /23, the third octet will always be even. It’s not possible to specify a network that goes from 192.168.1.0 to 192.168.2.255 without going to a /22, and that would be 192.168.0.0/22 and would range form 192.168.0.0 to 192.168.3.255