FPO: Can some one explain the numbers in FPO.

I see the stack trace most of the time with FPO and Non-Fpo words in it.
OSR in its NT insider magazine (which I am really fan off.) has
published couple of debugging crash dump articles, but never explained
what these numbers in FPO mean. I believe FPO means Frame pointer
omission. But what does those mysterious number in mean?