The template stack will show (not necessarily ) all FWs that you may want to include for that stack.
But check marking those few FWs that belong to the stack, then you are essentially pushing to that list.
So...if your company had 10 FWs and you wanted your GLOBALFOUNDRIES template to be used by all 10 FWs, then you would select all 10.
Now, if you wanted to remove, say, (2) PA-500s from the stack, you would uncheck mark them.
Now do you still have 10 FWs? YES... but 8 would get the stack pushed to them, and the PA-500s would not (because there were unchecked)
My stack, has 1 FW in it.
The stack has zero FWS in it.
Now I delete my FW from Panorama (already have removed FW from any device group and template)
How can I assist more?