@cnixon14 The forum software makes it really hard to embed a regex, so this will take a little work...
Use Match Version Number or Higher.bash to generate a regex for version 5.6 or higher.
Then change to a single Criteria:"Falcon Sensor Version" Operator:"does not match regex" Value:"The regex generated by Match Version Number or Higher.bash"
You should probably switch the modifier to "does not match regex" instead of the "is not" modifier. And use something like ^[5-6].*
That should find any version that doesn't start with a 5. or 6.
You might have to add in some other criteria in case the extension attribute you're using returns something like Not Installed, as mine does, or if it's blank (i.e. a machine hasn't checked in with new inventory in a long while)
Edit: @sdagley beat me to it. Same idea.