well that number is probably before the cell carriers add their own software to the device. when you hard reset or first turn on the phone when its new out of the box, it loads up THEN sprint has their own software thats loaded up.. THAT extra software eats up some memory, hence why you notice a little less.

if you search here for "bloatware" you will see what programs are loaded up. you can stop this process by soft resetting the phone when you see it say "loading customizations...." if youd like...