Overclock issues

[Gammawolf]

Ok, so a first time overclock, i've got a e6300 2.8ghz, currently at 3ghz but i noticed whenever i use real temp it shows the right speed for a few seconds then it displays a bus speed of 20mhz more than what i've set it too (286). When i load up cpu-z it just goes straight to a bus of 308.9. I dont understand though its set at 286

 

[Gammawolf]

But i set the bus to 286 why is it 309? just wondering whats going on as i've not done this before.