Network Discovery Question (Opmgr MSP)

I added network 10.128.128.0/20 to be auto-discovered. It did discover the network devices just fine. However, it also added many unmanaged /24 subnets that fall with the larger /20 network range that was specified (see below). Is this normal behavior? I'm not sure why I would need the smaller network? Can I delete them or should I just ignore?

10.128.128.0 255.255.240.0 managed <-- this is the /20 I added
10.128.134.0 255.255.255.0 unmanaged <-- OpManager added all the /24's
10.128.135.0 255.255.255.0 unmanaged
10.128.136.0 255.255.255.0 unmanaged
10.128.137.0 255.255.255.0 unmanaged
10.128.138.0 255.255.255.0 unmanaged
10.128.139.0 255.255.255.0 unmanaged
10.128.140.0 255.255.255.0 unmanaged
10.128.142.0 255.255.255.0 unmanaged
10.128.143.0 255.255.255.0 unmanaged
10.128.144.0 255.255.255.0 unmanaged <-- just outside the /20 range above

Tip for RedHat users and large network discovery:

We did run into an issue during discovery of large networks when using RedHat linux as the opmanager probe. If you see this error message:

DISCOVERY: Exception while recieving response for IP XX.XX.XX.XX ... IO error sending PDU. Send Error: No buffer space available

in your discovery.log, then you may have exceeded the OS's ARP cache limit. Our system engineer reconfigured the OS and increased the limit and the problem went away.