Physical % complete (Activity % Complete)

Hi, I am unable to find the setting to change this.

1. In a new schedule created in OPC, when i have this column in the view or when i see it in the Activity Details section, it is automatically changing the % complete based on start and finish times when i hit the schedule button. I do not want this. I want this to be a % that I give it.
2. In a schedule that I have imported from P6, this works exactly how i want as in I will give it a value and when i hit the schedule button, it does not change as noted in #1 above.