You can use a subnet calculator like [link]https://www.ipaddressguide.com/cidr[/link] to calculate them.
The range you specified would actually be two cidr ranges, so won’t work directly.
You can create address objects on the FortiGate that’s are ranges (instead of subnets with masks) though and may be able to use the address objects.
Hi can you try in cli.
config router policy
set input-device "internal"
set src "x.x.x.x " -------------> Internal Subnet
set dst "0.0.0.0/0.0.0.0"
set gateway Y.Y.Y.Y -------------> WAN
set output-device "wan2"
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