How to solve the problem of the Shadow effect being cut off (seemingly out of bounds).

[Pyuahowaito]

Hello author, I encountered a little problem when using the Shadow (similar to the external glow of PS) effect, the shadow transition part was cut off (seems to be out of bounds) the look and feel is very unnatural, I can't solve it no matter how much I try, this problem has bothered me for a long time, I found that other author skins and your skin examples have such a situation, when I tuned to Shadow 10, it will not go out of bounds, but it is too light. if you are interested in this, please help me, thank you in advance!