Claire was looking at square footage... Fence line are per liner foot. Is this the NEW MATH?
Her point was that the same square footage (i.e. AREA) could be surrounded by a different footage (i.e. PERIMETER). She gave the example of two tracts of land that are each 100 square feet, but have very different perimeters. That is why one needs to know the shape/dimensions of the land before determining how much fencing is needed.
This brings back days of high school calculus and using differential equations to determine the min/max perimeter of a given area (and vice versa).