Adjustment for defrost control - GE Monogam

Question

I installed a new WR9X502 defrost part in my 8 yr old GE Monogram. The technician said they go out at this age, and suggested I could install it myself (which I did - very easy). However, he did not tell me there is a small adjustment hole that can be rotated clockwise by a s***w driver.
Question: How do I know how much to rotate that adjustment?