Tide/Water Level Correction

Just starting out with a Helix 9. Sorry if this is old news, but I couldn't find it directly addressed. I will be making sonar recordings and creating my own maps for the local reservoirs I fish the most. I understand the need to make corrections for the water level when it is not at the standard pool. However, I see that there is a way to enter this on the unit before recording and on the PC when the data is imported.
Is one better than the other?
If I make correction on unit during recording do I need to 'confirm' that correction when I import the data to the PC?
Can I skip the correction on the unit during recording and just make the correction during import? (Actually this is what I would like as the pool level is not normally posted by the time I begin fishing.)
Any explanation about how these two correction options work, and the easiest way to have correct maps is appreciated.
Thanks

I too have the same issue. A simple tutorial by the experts here would be awesome! (Including how to know how much your local body of water has varied from the last time you charted!).

This is a great question. Has anyone figured this out since the original posts or have some understanding of the issue they could contribute ? ?