I let my OCD get the better of me once I noticed that the gauges are different - One has a zig-zag to it and the other, not a.
Per Google and someday buy me a beer at a Convention, lol:
"In essence, the two gauges serve different purposes, enhancing the overall user experience by providing redundancy, clarity, and different ways to monitor fuel levels, according to a VEVOR product listing."
PS---In different lighting, and it was said, to enable more certainty in knowing the fuel level.
PS2---I now have an idea of what this is, anyway! I used think 'diesel' = Diesel engine, only, lol!
Grow BIG---
eg