1st change User Mode under the Setup tab to Advanced ...
Then farther down in same setup tab is "Depth Offset" for adjusting digital depth readout to compensate for xducer depth in water ...
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"Water Level Offset" under the Chart tab is to adjust map spot Soundings to match actual water depth observed in digital depth readout ...
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"Depth Offset" should always be adjusted before adjusting "Water Level Offset" ...
Rickie