From The Mana World

Warp sizes are nonintuitive. This article aims to help describe them.

Width and height work basically the same, so only one will be described here. What applies to west, applies to north. What applies to east, applies to south. Here is an overview of how it works:

West East
Tiles 4 3 2 1 0 1 2 3 4
Width 6 4 2 0 -1 1 3 5 7

So, a width of negative one restricts the warp to the column of tiles specified by it's location, while a width of four extends it three tiles west, and two tiles east. A width less than negative one makes the warp disappear.