Groove Agent SE sample editing issue

Objective: layer two kick samples on a pad and adjust volumes to mix them how I want.

I found a demo of how to do this here:

https://youtu.be/clPfqiMT0bY?t=5m45s

My screen looks exactly the same as this and I have clicked the little PAD button to change it to SEL which according to this clip should allow me to adjust the volume of each sample separately and I also changed from velocity to layer…

The problem is it doesn’t work - if I adjust the volume knob it changes for both samples together as though the PAD/SEL toggle button isn’t working.

Is there something esle involved not explained in this video?