Can you elaborate a little more? Unless I’m totally not understanding what you are asking. I’m guessing the images are too big/small when you edit but when they are posted they don’t look like the size they should be?
Since we’re not sure exactly what you did when you added images and got different results before, I’m going to suggest that you try using our gallery feature instead of doing whatever was producing inconsistent results before. Here are the instructions showing how to setup image galleries: http://en.support.wordpress.com/images/gallery/