Monty - first of all muchand didn't mean to be an ass during the tourney.
2.5:1 = 28.6% (1/3.5) equity. Then you have to calculate your hand vs. a range in which pokerstove helps you out with. The ranges have been defined already.
I think I see your problem. You just divided 2/5 but that's not how you get to percentages. I hope you can see how I did it.