A very similar concept to my radius jig, only this is a chamfer instead. The length written on them is a measure from the corner of the board to the edge of the template. See the diagram in the 3rd picture. As an isosceles triangle, it is the leg length, not the hypotenuse length.
For more information, see my blog post on the subject. https://kiltedcraftworks.com/2019/01/19/corner-chamfer-router-template/