[codeduck]

  Mapcodes are a free, open way to make every house or location on Earth 
  addressable by a short code. With nothing else except your mapcode, 
  for instance, a navigation system will bring someone to within meters 
  of your front door.

So what happens if you live in a multi-story block of flats?

[bitJericho]

I think this is to improve on postal codes, not address multiple-person dwellings. The flat/apt/suite number would take care of that.

[micheljansen]

Presumably, for car navigation, that doesn't matter (that's what the address is for).