Clarification on bpd and ipd clauses needed #1283

Hi all,
I am struggling to understand the what the clauses at https://w3c.github.io/ttml2/index.html#style-attribute-bpd and similarly at https://w3c.github.io/ttml3/index.html#style-attribute-ipd, where the spec says:

If a tts:bpd attribute is specified on a span element and the computed value of the tts:display property that applies to that element is not inlineBlock, then the semantics of tts:bpd only apply when computing the block progression dimension of any applicable background color or image; however, the dimensions of the content rectangles of the generated areas are not changed.

(likewise for ipd, leaving out the quote for brevity here)

It's clear what this means in case of the given examples, where the spans are set to be displayed as inlineBlock, but I do not yet understand what it means if they were not inlineBlock(s). Suppose the span has a backgroundColor assigned. What does the above quoted definition mean for the (backgroundColor-filled) rectangle that is to be painted (by a renderer)? If the assigned bpd/ipd is larger (or smaller) than the respective (computed/resulting) content rectangle's dimension, should the background-area grow (or shrink) and overlap with the adjacent content rectangle (if the assigned bpd is larger than the content rectangle's bpd)?
Would it be possible to provide an illustration?

With kind regards,
Erik