Looking at the depth displayed, it seems inaccurate. I connect the unit either to my bow trolling motor transducer or console wires which connects it to a transom transducer.
How do I know if either is showing the correct deoth especially the transom mount seeing as how the transducer is flush to the boat bottom which is a few feet below the surface. The Tr.M. transducer connected to the motor is also lower than the surface by about 2'.

What I did recently was to mark my anchor rope with zip ties every foot to a depth of 8' to test accuracy. Should be able to try it soon. I got to be careful getting close to rocky shallow bottoms when using the gas motor not knowing if the depth is 4' or 2'.

Add the depth the transducer is submerged with the Depth Offset menu.

I took a 7' PVC pipe with me today with 1' measurements printed on it using a marker. It showed a 1.5' depth difference (deeper) than what was on the screen for the trolling motor transducer. I'll do the same for the stern transducer.
(I unplug the sonar from the transducer I'm not using.)

Did you take into account how deep the transducer is in the wayer