One thing you could try is this.
Just borrow a friend's timing light and check the degrees BTDC with his light. (For instance, his light might show timing is at 5 degrees BTDC.) Then, shoot your timing light and adjust the knob until the timing mark shows dead on for zero. Then temporarily put your sticker back in place with the 5 degree mark at the indicator on the knob. You can then re-check yours by setting the indicator to zero and see if the timing reading is the same.
