Problm in clock speed of gpu

[dabas007]

i have a saphiere 1gb 6770 its default clock speed is 850 but my amd catlyst show only 775. and maximun is 800 but i read its easily oc to 9oo mhz.
my system spec. intel quad 8400 4gb ram corsai vs450w psu

 

[the great randini]

the default on the website is 775 it must be an ebkac error?