Normally the material is butted against the poly fence and this automatically creates a 1” tenon. In order to change this length we have to make a different stop for the wood. We simply inserted a screw into the poly fence.
Be sure that it lines up the precut grooves in the tenon mitre block.
We adjusted the screw so that it was 3/4” from the fence thus leaving us with a 1/4” tenon.
Butt the wood up against the screw stop and run your piece through.
If you want a different tenon length simply adjust the screw.