Enter 15 minutes of zumba. Exactly how many calories off are we talking about here, anyway? Does it matter?
Remember all values are estimates. So you simply do the best you can, enter what seems the most right to you, and don't try to get it "exactly right". There is no such thing.
You might find those 15 minutes of zumba is only 100 calories. If you're going to one zumba class a week, that 100 isn't going to make much difference whether you track it and shouldn't have, or don't and should.
(And remember you carry on burning, and the ST burns *something* anyway, so it won't even be the full 100 calories 'off'. This is a no-panic deal. Do what you feel is right.)
Deb, in New Zealand