Why does Hillary get 19 delegates from Nevada Caucus and Bernie gets 15 when the popular tally is 52.6% to 47.3%?

Sorry if this is a silly question. Though after many attempts at googling how delegates are counted I just can't find a source to explain this to me. I also called a Bernie Sanders hotline and the phone rep didn't know how they tally up the delegates either.

My question is why aren't they receiving almost the same number of delegates in Nevada and Iowa when the popular vote is nearly tied in each of them? Is she winning more precincts or something? How do they award these delegates?

Thanks