I found this question: on StackExchange
I have the same problem. I have a Illustrator image which has 25x25 px and no matter how I save or export it, it is at least 71x71 px when exporting as a PNG, I tried saving the artboard or Save for Web, nothing works. I tried it for 72 dpi or 300 dpi, it doesn't work.
Anyone know how to do that?