Well, considering I have been to Five Guys, I suppose I am just not a normal human. A small fries is easily consumable by one person. Does that mean I advocate that? Not at all. When I do go to Five Guys (which isn't often), I will usually eat half the normal fries.
I suppose for reference sake, when I go to the movies I can finish a large popcorn and large soda from the time the first preview starts until before the actual movie starts, so about 15 minutes. I also drink a bottle of wine (750ml) in about 2 hours. If a 120lb Japanese guy can eat 70 hotdogs in 12 minutes, you guys need to man up once in awhile.
Well, here's a reference: I hit up Five Guys with my kids the other day. The small fry I received filled half a lunch-sized paper bag. That's a crapload of fries to go with a burger.