It is certainly not normal, though I've personally seen this on many Celeron models (like the 900 and the E3300), and it usually turns out OK anyway.
I've had a minor incident when it mis-showed the frequency calculation, but in that case it was related to the motherboard not supporting OC that well...
Just as an FYI, overclocking even though the frequency-calculation is incorrect usually don't result in any damage. But would be very careful if I were you.