Hi Jose,

you probably didn't scroll to the right in the statistics view. Also note that you can select if you want to see the data for one level or all levels.

Besides that it is really difficult to answer your questions.
Labels are deduplicated, so each different label is only saved once in an IMG and the objects with that label are storeed with a ref.
The size required size is that for the RGN data (which discribed the geometry) and the NET data which contains the labels, house numbers
and other data and finally the NOD data which contains routing data.
Garmin uses all kinds of compression methods to reduce redundancy, so it's  difficult to see an effect when you make small changes.