To prevent a device that is part of a larger cidr block from being discovered Add the host address as Excluded CIDR block.  To do so:

 1. Navigate to Settings --> Settings --> CIDR Blocks
 2. Enter the IP Address of the Device with a /32 mask
 3. Click Exclude

Note:  If the device has multiple interfaces that are part of other CIDR blocks, you will also have to exclude those interfaces

You can also import a text file like :

6.40.40.10/32    EXCLUDE

6.40.40.23/32    EXCLUDE