Making Monsters With Correct Coordinates

I'm trying to create units but I'm having difficulty determining the size the canvas should be. All units have different sizes and different coordinates. I'm trying to make it so that the number box [##] doesn't go into my sprite. If it doesn't on the left side, it does on the right side. How do you determine what size an image should be.

Hello Voyager!

The stack number display is actually not determined by the size of your image. Instead, you set it manually in the creature frame information. See http://projectironfist.pbworks.com/w/page/57740979/Controlling%20Creature%20Animation, specifically the 'stack-number-display-facing-right-xoff" and "stack-number-display-facing-left-xoff" fields.