My Answer(I would stick to this one) ->
Jenny - Donuts - Boxing - 20
Tim - Cookies - Karate - 13
Carl - Muffins - Treadmill - 27
Olivia - Popcorn - Walking - 34
Rachel - Pretzels - Yoga - 24
But it doesn't quite fit with clue 6.
#Other Possibility ->
Jenny - Donuts - Boxing - 20
Tim - Cookies - Karate - 13
Carl - Popcorn - Treadmill - 27
Olivia - Muffins - Walking - 34
Rachel - Pretzels - Yoga - 24
But this one doesn't fits with clue 4(until there is a mistake in clue 4).