Question of saving icons...

I'm just getting this problem now. Alright, so I make an icon and I save it as .png and check my file size and it's under 40K, but then when I upload it, the size turns out to be 70+K. I try flattening the icon, saving it as .jpeg, but it still uploads them to more then 40K. It's weird though. I was looking through my uploaded icons, a few icons I made that were origanally b&w were good, but some other b&w icons were over the 40K limit. Then a few high-res. pictures I made icons out of were under the 40K limit, but some others were over. I don't know what to do, like do I save it as something else? Or what?

help =(

ETA
I use Photoshop Elements for my icons.

And here's a screen cap to see my dimentions and all.