Now this is important: If the y offset value is set to 40 you have to set the Projection Map node`s Y-origin to  -0.8. The logic behind is that because the Multiply node on top of the function is set to 50 you have to divide the values you set in the Offset node by 50, which makes 0.8. But for the Projection Map node`s origin you need to set it to a minus value (for which I have no explanation). Anyway this way it seems to work. Tested it with different values and it always worked as expected.

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