Hi, welcome to the Spine forum!
The windmill tutorial was made with an older version of Spine, but the specification for local rotation has been changed since 4.0, I think that is why you are confused.
To clear up the confusion, check out Windmill's completed projects, accessible from the list of Examples on the Welcome Screen:
As you can see, the rotation curve of the windmill-blades-front draws a straight line that rises to the upper right in graph view. This is the correct curve for one rotation in 4.0 and later. Actually, Spine older than version 4.0 could not key values greater than 360 degrees in the value of rotation, so you needed to set the four keys: 0°, 120°, 240°, and 0°. However, it is now possible to key values beyond 360 degrees while the local axes are selected.
If you check the values of the keys on this curve while selecting the world axes, they display 340°, 111.74436°, 240.66316°, and 340°, while selecting the local axes, they display 0°, 120°, 240°, and 360°.
When world axes are selected, the rotation is limited to 0-360 degrees because it indicates which direction the bone is pointing in world coordinates. The values while selecting the world axes show the final values affected by the parent bone's scale and shear, so there is a halfway value like 111.74436° in the windmill project. (For your information, the number of decimal places was too long in 4.0, so rounding of values has been improved in 4.1. )
Please refer to the following page of the user guide for more information on the differences between the various axes selected:
Tools - Spine User Guide: Axes
