That's right. Just as "contains 192" does not work, this makes it useless in this case.
192.0.0.0/8 would match "192" only in the start of the address, which is what OP wants I guess.
If we have two addresses: 192.168.1.2 and 220.127.116.11, how would I match these two with one rule containig 192? No way. If I write two rules, they are linked with AND and I would not be able to write several conditions to match "192" in the four possible parts of the address.
This leads us to my problem with "OR"
Anyway, this would not be easy even if I had the chance to write 4 conditions because what this would require is something like *.192.*.*