This should make things a little easier. That is, if you have a 2820 or the like...
Go to the Main Menu and select 'Settings'.
Then select 'Map'
Then press the down arrow for the next page down.
Select 'Map Data Fields'.
Select 'Thin', then press 'Next'.
Select 'Custom Fields'.
You can configure your screen however you'd like, obviously.
Once I was done, this is how my Navigation Data Fields settings looked.
...and my Non-Navigating settings.
The first time I tried getting 'Speed' up in the top field, this is the way the screen was configured. Yuk! I didn't want to share that top field with 3 lines of information, so I had to change it. Press the +
Now there's two lines of data ... press the +
There, that's better! 3/3 means that you only have 1 line of data in that field. You can experiment to see what you like. IMO, anymore than more line of data and the information becomes too hard to read at a quick glance.
I hope this helps. No sense in all of us reading the manual and figuring this crap out.