The new PIC is 8722 not 8720 and the processor runs at 40 MHz but the prescaler examples are assuming the procesor is running at 10 MHz.
This is the actual Pic18F8722 data sheet:
http://www.kevin.org/frc/PIC18F8722_ds.pdf
That is just he C18 complier library to help with timers and stuff but not the actual Pic data sheet.