Nate Thanks Nate, you are right, it is Photoshop not setting the origin properly.
For others having similar issues - "To change the rulers' zero origin, position the pointer over the intersection of the rulers in the upper-left corner of the window, and drag diagonally down onto the image"

Describe:
1) Create a composition in Photoshop
2) Create grid lines (in this example 1 vertical 1 horizontal so they intersect in the middle-bottom side of the composition)
3) Export composition using the provided Spine script (PhotoshopToSpine v7.31)
4) Open Spine > Import Data > WhateverYourFileIsCalled.json

Result: The opened composition has the root bone aligned to the top-left instead of middle-bottom.

Spine version: 4.1.23 Pro

Misaki Thank you for the answer and documentation

First I'm not the tech side of my team so excuse my lack of knowledge but I'm passing further the question that I've been asked.
My curiosity is regarding bones and CPU usage, for animations made in Spine then imported into Unity.

Is there a difference in CPU usage, between bones with 0 length and bones with >0 length?
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We're trying to optimize characters and buildings for a 2D game as best as possible without sacrificing too much detail.