Only if the map is finished. The OP may want to add more stuff to the left or above what's already there, and there's no room to do that.
But yes, once the map is done, if there's still a lot of empty space above and to the left, move the map in the same way, to remove all the emptiness, then reduce the size to remove the emptiness to the right and below. But make a copy of the map first in case you get the numbers wrong.
Avoid the temptation to plonk your usable map in the middle of a very large sized map and leave the outside blank, as bigger maps require more processing so will affect your game's performance.