How to filter Group Policy based on computers

Hi,
I’m trying to restrict a GP, with a startup script that installs a software, to only some computers.
The computers are currently in different OU’s and hence I would like use Security Filtering based on Computer Group.
After reading material on technet etc. In the Scope tab of my Group Policy, I removed the ‘Authenticated User’ and added the computers group that I created ‘Test-Computers’. (which has two computers that I want software installed on regardless of who logs on)
But when I use Group Policy Modeling it shows the GP is not applied and says it was denyed.

Can anyone recommend or explain how to filter GP based on computers ? Creating a new OU is not an option as there are already a number of sub-OUs.

Thanks.