Extra letters on display odometer screen?

It's my first time in 10 years. Such issue never comes before.

If they are trip counters, how to select a and b? There are no control buttons on my steering wheel? Is it a light bleed?

What would be the likely causes of such voltage bleeding on the screen?

Actually, the issue slowly dimmed away after about 5 minutes, and everything is normal again.

Can high voltage for instance 16 volt likely cause of such issue?
Or, can such issue arises because of car is parked under constant raining almost 28 days in 1 month in my location at temperature about 19 to 22 degree?

Nope. Not exactly. Last time, my car battery drain and in emergency I recharged with home inverter until it's full. I reconnected the battery to the car without the key inserted as is supposed to be. But, I don't think this is going to create the problem to the display since the battery was reconnected with the key removed!

Took out the instrument cluster panel and kept it under the hot sun for continuous 5, 6 hours to see if any moisture etc, is causing the issue.

Reinstalled the cluster and the battery successively.

1. Key is at on or engine running, yes, the screen is normal.

2. Removed the key and wait about 1 hour, repeated the same checking process, yes, still the screen remains normal.

3. Now, this morning (after about 18 hours), I repeated the same checking process. I'm very disappointed to find that the issue still persists with those letters appearing vividly clear now, and like before, they dimmed out slowly after 5 minutes.

4. The fact that those letters dimmed away slowly is suggesting me that. They are controlled by a capacitor which discharged itself when key at on or engine running, and ultimately, those letters dimmed away. And, capacitor recharged itself when key removed. So, how to identify that capacitor or alike is leaking to cause such issue.

Thanks a lot.

Please provide the complete whole circuit board diagram.

Yes, with your help the odometer is normal again. Thanks so much Indeed.
(I dissembled all the instrument cluster panel and even the gauges pointers and reassembled all.)

However, meanwhile, tank is fully filled and the fuel gauge is sometimes stuck at half mark but never to zero mark.

Reinsert the key as well as resetting by removing the battery doesn't work.
The gauge sometimes shows full, sometimes halfway.

Even when the key is removed, sometimes it stuck at halfway or full mark. This is very surprising!

There is about 1 v at the wire of the fuel sending unit which shows voltage is ok. For 12 v, it will be fuel empty. On voltage reading, fuel system is ok.

Do I have to recalibrate the fuel gauge meter to half so that it will go to full when key at "on"? I have recalibrated all the gauges including fuel gauge to zero mark and all work normal.

Why this issue happen intermittently especially when key removed?