CPU on 12" PB 1.58ghz?

[California]

When I go to about this Mac on my computer, it tells me that CPU is 1.58ghz. Is that normal? It's a 12" PB.

 

[Josias]

My brother iBook is a 1.07 GHz G4, but it sais 1 GHz when he bought it from Apple. Just like 1.25 GHz is abbreviated to 1.2 GHz. I think it is the actual clock speed, or were we a bad boy and overclocked it tinyly?