How these timer values are derived?
For mode 0:


8192 is the number of ticks available before the timer overflows (13 bit mode). 
Assuming 12MHz clock, the timer will be  clicking at 1 MHz. 
One tick is equal to 1 us
Let us compute counters for 5 ms
Register value is 8192 - 0.005/1u. 
So the counters should have value of 3192. 
Timer higher byte = 0x0C
Timer lower byte = 0x78