I’ve had it happen several times. Here is a quick video of it. Is it an undocumented indicator, bug o4 something else?
I have that too. Though you describe it better. 
http://community.anovaculinary.com/discussion/349/significance-of-blue-lit-wheel#latest
Glad to see I am not the only one. What’s curious is if you look at my video I scroll back to my target temp and then back down to try and replicate it repeatedly and my second try did not. Which is why I’m wondering if it’s a glitch.