How to use equation from chart as a formula to return a value

I'm having quite a bit of difficulty (despite googling) using a formula on a chart to return a value along the line. The line is a 3rd order polynomial, though this shouldn't matter.

In the attached xlsx example I'm attempting to return the outflow for reading 155 AHD. I have provided sample data, and a chart which I think is set up correctly. This is something I've never been quite able to get a handle on in the past, so all help would certainly be appreciated.

Thanks

2022-03-10 12_24_58-Window.png

Thank you

Would you mind explaining what that formula is doing / how you made it work so I understand how to use it in the future?