how do i properly add alpha channel/layer mask?

Hey guys,
I'm just curious how does 2K and other patchers create their green texture.. Because when I do the normal way (the same as JaoSming's tutorial) it doesn't look properly like 2K's and other patchers'.. Here are LeBron's cyberface's green normal maps in the attachment..
The one on top is 2K's and the one on the bottom is mine.. I edited the default green bump and can't manage to return the alpha like the original..

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can someone just help me do a green normal map for a jersey i have here? I have the author's green normals but i edited the main texture so I should also edit the normal but I have no idea on how to make a proper alpha channel for it..

iirc from my tutorials the alpha was just a certain shade of gray