Speedometer not at Zero

on my Duster, I looked at the speedo and there is a fine spring before it gets to the needle. I found if I played with the position of the piece of metal that anchors it, I could get it to return to zero. Also I could get the speed more accurate.
I used super glue to hold it in the position I wanted, then when I needed to adjust it, I would get a dentist pick and us it to free the metal, it chips away somewhat easily, move it a couple millimeters and re-glue it.
It was trial and error. took many attempts to adjust it, now I am only a couple mph off and I now leave it alone