speedometer circuit board SCREWS?

I recently opened up my instrument panet to fix my odometer, so i saw 2 adjustable plastic screws at the back of my speedometer, i did not know what do they do so i turn them and check to see if the problem with my odo is from them but it was not so i get it to some speedometer fix and repair shop and he fix my odo but i still dont know what the 2 small plastic screws on the back of the speedometer circuit board do !????
my car is a 91 xj with electric speedo ?
any knows what they are and what do they do ?

no its not broken just a little hesitation in speedometer needle !

A picture would be helpful. I've had my fair share of clusters disassembled, and no plastic screws come to mind.