In the HRRN scheduling, priority formula is
P = (W+E)/E , where W: waiting time and E: estimated run time.
CPU finds the job that has highest priority value and does that job.
However, the formula is equivalent to P = 1 + W/E. If we just "minus 1" and make a new formula P' = W/E, the order of jobs does not change.
So the question is, why do we use P = (W+E)/E rather than P' = W/E? Is there any specific reason (like P must be greater than 1)? Or are they just using the original formula since it was made?