Start typing the name of the job(s) you want limit the action scope to (or from, see Invert below) and options matching your text will appear.
Invert can be used to switch between an inclusion or exclusion condition execution.
When invert is not selected, default, then the condition will only match builds if the build is off one of the selected jobs. When invert is selected, then the condition will only match builds if the build is not off to any of the jobs selected.
Next: Getting Started