Speedo Swap And Digital Mileage Discrepancy

I've recently purchased a Bonneville Newchurch, the Speedo on it was just a single dial with no accompanying rev counter, it also had what seemed to be a button missing on the side of it, so I decided to remove the speedo to investigate. This is where the Saga began, whoever owned it previously has bodged a concoction of a speedo together (see photos), never have I ever seen such shoddy work.

So, trawled the Internet and found someone not too far away selling a dual clock set (which to be honest I think it should of had in the first place) and have been and purchased and fitted them.

Now to my issue, my bike has around 8k miles on it, the clock set I've bought has 14k on it, I did think (or at least hope) that the mileage was store on an ecu on the bike not on the dials itself, however it's now showing at the 14k plus mileage.
Is this something that can be rectified via a plug in ready etc? Maybe the dial needs registering to the ecu?
I know it has been done previously on cars so was just hoping lol

 

Thankyou for the answer, I'm not too bothered about the mileage as like you say if I have proof it shouldn't make a difference.
Just wondered if these bikes had the mileage stored in and ecu kinda thing, I have seen this on cars for instance a land-rover discovery I owned.