Whole sample playing after truncate

[Seamus Bottletop]

Hi
I'm a Tal Drum noob and I'm sure I'm doing something dumb, but this has been annoying me all afternoon and I can't work out a solution from the interface or the manual.

I've got a very long drum loop. I've moved the sample end point down to just one bar and truncated the sample.

Why is the whole sample playing (everything after the end point and the truncate) even though I've done this?

This doesn't make any sense to me at all as in any other hardware or software sampler that I've used moving the sample end point and/or truncating means nothing after that point plays when the sample is triggered...