The more digits in a grid
coordinate, the more precise
the location. For example:.

2579 - A 1,000 meter grid
square.

255797 - To the nearest 100
meters.

To determine your address,
start from the left and read
right until you come to 25, the
first half of your address, then
read up to 79, the other half.
Your address is somewhere
in grid square 2579.