So this is a system that swaps several minutes trying to work out what is in some fuzzy pictures, with many minutes trying to find your U2F key from wherever you put it after Google last asked you to sign in with it.
Ok... And which of my two keys (and two backups) should I be using?
I'm not completely certain, but I'm sure that leaving the key permanently installed in your computer's USB socket is not secure behaviour.
Still, it's at least better than having to dig out your phone, start the Authenticator app and copy across the six digit code. If you can remember the right one to use.