Clip attributes - change number of audio tracks

Changing the amount of audio tracks for a clip in clip attributes (in this case FS7 4K .mxf) has no effect.
I try changing from 8 to 2 and nothing happens - it's locked at 8 tracks of audio.

Beta 6
nMP D700 32GB RAM
MacOS 10.12.5

Cheers,

Mike Kelland

In 15 you need to select the trash can (hidden) logo to the right of each track and click on it.
Each track, one at a time.

14 it was SO MUCH EASIER. Just enter the number of tracks like you have done, and hit enter.

Not sure why BM made it harder to do ......