Why in game maker when I try to add or modify my jump height, it doesn't work?

Whenever I try to change the equation, the jump height doesn't change at all. Only when the value added to the y constant is negative the "jump" height changes. It teleports through the platform. Also the isUmbrella is just about if it decreases or sets the standard gravity.

I tried changing the variations of how the y constant could change, at first y-= 30, y+= -30, and finally y = y - 30. And it still didn't change the jump height.

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