Hi Tran,
For example, if you want 10 ms for the interrupt,
Timer clock frequency = Source clock frequency / 2u8Prescale
The clock is 16MHz so the time period is 0.0625micro seconds
Pre-escaler= 8
Clock by 2^8 = 256 hence multiplying the time period by 256
Timer clock will be 0.0625 * 256 = 16us
Time High =(10ms/16us)=625
vAHI_TimerStartRepeat(E_AHI_TIMER_0, 312,625);

For a better reference, please look at the JN516x Integrated Peripherals API User Guide
Regards,
Mario