If this a town in Utah that would be low. I considered the 15 I counted in a town of 80,000 in Alberta to be low, one of two wards that share the same bldg I believe.
You have to remember the amount of people that can go into a mormon car. It's a lot like the Philippines. It is not uncommon to have 12 people on one motorcycle in the Philippines. 55 cars in a parking lot could easily represent 1000 Mormons.
The LDS meeting house is across from the coffee shop I frequent on Sunday mornings. The front lot at the LDS was half full, the back lot was empty. I heard they are told to park in front to give the illusion of a big turnout.