MultiWAN firewall rules problem

[barchero]

First of all, i've configured my pfsense with a MultiWAN configuration.
my problem starts when a client in my LAN interface tries to connect in a HTTPS page

The solution that i'm trying to do is adding a firewall rule to put that client in a unique WAN
but when i put the IP (192.168.0.x) in the source field, the web enviroment returns a /32 netmask and i can't be able o change it.
By the way, i want a /24 netmask
Can anyone tell me a different solution or an explanation of why the pfSense web can't let me change the netmask?
Thanks a lot!

[phil.davis]

You are doing right. In that place in firewall rules you put a netmask (CIDR bit count) to indicate the range of IP addresses you mean. It is not the netmask that the client would have on the LAN.
To specify a single IP address it is 192.168.0.x/32
You can also specify "networks" that can cover parts of your LAN, OPT1 etc e.g.:
192.168.0.192/26 matches 192-255 (64 addresses in /26)
192.168.0.160/28 matches 160-175 (16 addresses in /28)