Are you asking about bend relief values, how much the material changes size between the bent form and the flat form?
It doesn't matter if you dimension to the inside or outside, the material goes through a deformation when being bent and therefore the flat pattern must be cut to allow for this. You need to understand what the neutral axis is to understand bend relief.
I have uploaded a good reference.

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• https://files.engineering.com/getfile.aspx?folder=8c700a66-176a-485b-b1a3-3

Thank you very much for the reference.

Thanks & Regards,
Sam

The sheet metal reliefs are meant for those corners where the two flanges meet, so it is weldable. The reason for making the corners different, for some, is that they like welding corners differently. So, you ask one person how they like to weld corners, they like a certain relief. Others like other kinds of relief. Some people like the corners to overlap, meet up corner to corner, etc. So, you would have to ask the customer or your lead how they like it on that particular project.

I am not the expert in welding the different reliefs, but, I know that is basically one of the reason for the reliefs, from my experience. If you're never going to weld the corners, then, you don't worry about reliefs.