it tells windows that you have a single set amount of swap space which is the fake memory that windows creates. You set them both the same so that windows won't have to resize your fake memory which causes a lot of reading and writing from your hard drive. Changing this number simply tells windows that it has a set amount of memory to work with instead of letting windows try to resize this space as it sees fit. As for what you want to set it too. Most people I know set it to 500mb including my self. I have heard of people settin it to less and being perfectly fine too. I'd suggest no less than 200mb though.