[MNDude]

I don’t think anyone took into account the width of the border...

If the border is 2 inches wide, don’t you have to take 4 inches off the total figure (unless if you are sewing the the horizontal and vertical intersections on top of one another.

[FredZarguna]

There are so many unstated requirements of this, it's a terrible problem. Because the thickness of the border is given in "units" instead of "square units" you have to assume that the questioner is only concerned with how many linear units the border has to be. It might be an inch, two inches, ½ inches, ¼ inch … who knows?