If you only want to scan the ranges submitted for IP Range Scanning, you must disable all other scanning methods listed in the configuration console under Scanning Servers\Your Server: Active Scanning, Workgroup Scanning and Scheduled Scanning.
You've named this thread "Active Scanning", so if this scanning method is enabled, please disable it. Also note that scanning methods work independently from one another. What you have submitted for IP Range Scanning does not affect what is scanned by Active Scanning. If you've submitted your domain for Active Scanning, but only submitted a few ranges of your domain for IP Range Scanning, Active Scanning will still scan your entire domain.
To delete unwanted machines that have already been scanned, select them in the configuration console under Lansweeper\Scanned Computers and hit the Delete button.