well, first I recommend that you try to determine how many working SCCM clients you have. You can run a report called :
"Count operating system versions" (the total will show you the total number of working clients)
If you run this and you only see 14, then the problem you have is simple; your additional devices on the network are not FUNCTIONING SCCM clients. That is, they might have the SCCM software installed, but for some reason, the clients are not working.