<!DOCTYPE html>
<div style="width: 200px; justify-items: right; border: solid">
<span style="justify-items: center">
<div>foo</div>
</span>
</div>
In Blink it looks like this:

So the <div>foo</div> is aligned to the start, ignoring both justify-items: right of the containing block and justify-items: center of the parent.
https://drafts.csswg.org/css-align/#valdef-justify-self-auto says
It behaves as the computed justify-items value of the parent box
But I'm not at all convinced that this case was taken into account.
In Blink it looks like this:
So the
<div>foo</div>is aligned to the start, ignoring bothjustify-items: rightof the containing block andjustify-items: centerof the parent.https://drafts.csswg.org/css-align/#valdef-justify-self-auto says
But I'm not at all convinced that this case was taken into account.