How to turn off GRT for Differential

We have a full backup job that runs 6x per week almost 24 hrs each job. I am trying to change the job to only run the full on Monday and differentials Tue-Sat. Problem is when selecting OK after adding the differential I get an error advising "The backup definition has an incremental or differential backup job that is enabled for GRT, but the full or copy backup job is not enabled for GRT".

I've searched through the Backup Options screen trying to figure out how to turn off GRT for the newly added differential but I'm missing it. Where is the setting to turn off GRT?

Thanks