In CIDR notation, /22 = 11111111.11111111.11111100.00000000 so you have 10 host bits, i.e. can have 1024 total hosts (but the gateway and broadcast come out of that so 1022 useable) on one supernet with addresses from 192.168.0.0 - 192.168.3.255.
You are using a major class C address, which has a default mask of 255.255.255.0 which is /24 (i.e. 24 network bits and 8 host bits). You borrowed two bits from the network portion, hence /22, to increase the host number from 2^8 to 2^10.