Why does the iron rust with less salt For my school project I was going to measure the rate that salt has on the rusting of iron. 

To do this I set up an experiment where I had 15 beakers containing 200 milliliters of distilled water. I poured into the beakers varying moles of salt $\ce{(NaCl)}$. I had $\pu{0mol}$, $\pu{0.25mol}$, $\pu{0.5mol}$, $\pu{0.75mol}$ and $\pu{1mol}$ of salt. So now there are three beakers for every concentration. I then put a iron nail in every beaker, put plastic wrap over them to stop some of the oxygen flow and left it be for 10 days. 

What I was surprised to find was that the beakers with no salt in them had more rust than the one ones that had. It was exactly the opposite of what I expected would happen, and I can't find a website that explains how this occurs. Does anyone have an explanation?
Corrosion is a balancing game. In this case, by covering the beakers, you have limited the driving force for oxygen dissolution by limiting the amount of oxygen available to dissolve into solution and then the higher salt concentrated solution is able to further minimize the amount of oxygen that can be dissolved and participate in the redox reaction (as explained in the linked question's answer).