When was that map created? I don't think I would mind a Terraria tracker saying "You have spent x hours on world example1, you have spent y hours on world example2" etc.
Similar to how in Albion Online I could watch my different characters and the game would say how many hours etc. I've spent on each character.
It looks like you have dug out entire parts of the map...that there are vast empty spaces.
Is that correct?