It makes all sense if you understand the conventions used in Brazil :

1) the building has an underground parking floor (G1 - subsolo means sub-soil, underground). But blind people do not park cars, for them it’s more important to know that they’re one floor below street level, so “-1” for them. In case of any emergency, they know they must use the stairs upwards, it’s not useful for them parking this or that.

2) next it has street level, “0” for both blind or seeing people.

3) next it has 2 more parking floors, garages 2 and 3, for drivers, but 1 and 2 floors above street level for blind people.

4) the following floors follow the convention of numbering the office rooms 100 to 124 in first commercial floor, 200 to 224 2nd floor, etc. Again, for blind people it’s more important to know they are 4 floors above the exit to street, so they will not descend one more floor into underground garage in case of fire or earthquake (there are no earthquakes in Brazil, just an example that would work in other countries).

Hope that helps.