If you've defined the custom width and height, you always must define the gfxwidth and gfxheight, with some NPCs the calculator does not work because it uses algorithmic animation (framestyle is ignored by the NPC's algorithm).
You always can open your npc-*.txt file with the editor and preview the generated image if it's wrong, and fix the problem by changing the size values:
Where red rectangle is - is a collision box (physical width and height values):
