distance between two addresses

The formula is just an approximation and certainly is not driving distance, but crow flies distance. It also works best at he geographic center of the USA and will utterly fail near the north and south poles (not much demand for distances for Polar Bears or Penguins). It's best used to rank results according to approximate distance.  The "exact" formula would require advanced trigonometric non Euclidian functions which do not exists in native Quickbase.  

But all kidding aside, if you are using it mostly in certain part of he world, it can be adjusted to be better as those values of 69 and 53 refer to the distance between the integer Lat and Long lines in your typical locale.