E11 Speedo troubles.

[Exbiker1990]

Hoping to call on all your collective wisdom here. 

I'm having some speedo troubles with my corolla. It's constantly reading 20km/h above what it should be. I figured it's the clocks rather than the sensor. I tried getting a replacement from the breakers, but it wasn't working right. There's a code on the actual speedo dial. E55-A and the one I tried putting in a was a E55-c one. How much does that matter? 

Am I barking up the wrong tree? 

 

Any help would be appreciated. It's doing my head in.