Can't change 'relative to' for fixed element

I would like the image (of the iPhone) in my hero section to be relative to that section, not the body.

But I can’t work out how to change it. ‘Relative to’ is fixed to ‘Body’ and can’t be changed.

Thanks in advance.

Here is my site Read-Only:

Steve, good question. From my quick review understanding.
Fixed is removed from the flow of items and placed in the viewport.
I think you want absolute if you want to attach it to a relative or sticky.

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