I think he's talking about the distance scale.
You can display the grid in the terrain editor (hotkey G) : there is the largest yellow grid which is 512 large, then the medium white grid which is 128 large and the smallest grey grid which is 32 large.
Most of time, destructables and doodads are usually 64x64 sized minimum but you can create custom paths 32x32, regions are 32x32 sized minimum as well and units has a minimum collision radius of 8.