If we are truly talking about the Suzuki MFG4 (its a square colour digital gauge with rounded corners as shown in the video linked below) then they have 2 separate ways of showing fuel info.
One is from the fuel tank sender, and it will only show up on the bar graph. Same as a analogue gauge that just moves the needle. Its is totally dependant on the float in the tank. You can set it up by inputting tank size and then calibrating by starting with an empty tank and then adding bit by bit and setting it at various levels as you go along. Or, you can just go with the standard calibration, its usually good enough. But thats never going to feed into distance to empty data etc.
If you want to show fuel level from the tank you are probably going to have to disconnect the analogue gauge and take the wires from the tank sender unit direct to the SMG4 harness.
The other fuel info this gauge gives you is a figure for fuel used. It will ONLY count upwards as fuel is used by the engine.
You can only reset the fuel used figure to zero when you fill up. That’s all. (Note the earlier Suzuki SMIS round digital gauge could give you fuel used, fuel remaining and allowed you to add fuel if you added some but didn’t fill up).
Here is a link to a really good video Suzuki put out back in 2015 when this gauge was released, tells you pretty well everything about it.
https://www.youtube.com/watch?v=IdghHrBpyWg
If you want trip fuel used then you would be able to get it on some MFD’s. For example I can get that on my Simrad GO7, you would have to have a NMEA2000 network and connect both the SMG4 and the Simrad to the network.