FourJacks,
Ok so it is saying that the player has 4087MB of storage and is 87% used. Which gives you about 532MB free plus the 500MB or so in files and firmware, I would guess your chip is a 1GB true capacity. Keep us informed I would be curious to know. If you get brave and want to know for sure take the back off your player and check the largest chip number against this list
HERE.