Canvas Size not working correctly
I want to add a border to an image by increasing the canvas size in such a way that it is increased by, for example, 1000px on three sides but by 1500px on the bottom. I have previously had no issue doing this. Today it makes the increase by putting the image right up against the top edge.

This results in:

which is quite obviously NOT what I want or need.
If I try this instead:

It results in this:

which is also no use!
This feature was working yesterday! Any tips gratefully accepted.
(I'm working on a single layer...it's the only way I can get the canvas extension colour to work - if I have all the layers there I can only have white.)

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