cant get a picture from my rrd db

hello all
i am new to rrdtool, and this ios my first try.

i have problam getting the graph to work i keep getting 0X0

i want to graph how many downlod a file had.

this is what i done :

1- rrdtool create filedown.rrd --step 300 DS:file:GUAGE:600:0:U RRA:AVERAGE:0.5:1:1200
2- then i make a small script that runs in cron every 5 min and update filedown.rrd.
when i do rrdtool info filedown.rrd i can see that it is realy updating in the last_ds and time.
i have a few qustion about why in the value i see 6.38479 float number?
and not the data i insert witch is an intger and i see it in last_ds

second why i keep getting 0X0
when i use the graph?

any help will be appreciate

thanks lady and guys