Right now I'm using,
<abbr title="11,201 bytes">10.9 KB</abbr>
There's no exact tag for what you're looking for. I wouldn't use an
<abbr> since they're reserved for abbreviations and may affect some web-crawlers, etc.
There is a good list of HTML tags here for reference.
However, for your use case I would adopt a custom-styled
It still supports the
title attribute so the tooltip will appear nonetheless.
If semantics are a concern, consider looking at adding
aria-label attributes so your HTML is up to the ARIA spec.