Approval Rule - Only on certain value

Hi Team. 

I have a VA that i am using and i have also assigned a PGV to that VA. The values that can be used for example are 

2GB

5GB

10GB

15GB

I also setup a Workflow with an approval rule. Is there away to only fire the approval rule if 5 , 10 or 15GB are selected and not fire one if 2GB is selected? 

Cheers

Craig