David,

I notice that no one has replied to your query, so I'll chime in with my recollection of how to handle this situation. For the record, I find there's rarely any useful information available via these "hover" (known more formally as "mouseover") controls, but sometimes there can be. Note that I can't test what I'm about to write because I don't have any mouseover items in front of me.

So, keep focus at the spot where JAWS has alerted you to hover. Press control-JAWS key-numpad enter, all three at the same time.
JAWS will announce that a change has been made at a certain line number.
Press j followed by that number. JAWS will read the change.
To return to your original location, press shift-j.

I hope this is accurate and, if so, that it helps.