It appears my understanding of that word was faulty. I always thought it meant something along the lines of first-rate, I didn't realize it had such a specific meaning. TIL, I suppose.
No worries, the majority of people make that mistake.
pe·nul·ti·mate/peˈnəltəmit/
Adjective: Last but one in a series of things; second last: "the penultimate chapter of the book".
To quote Murray Walker, an F1 commentator, "they're on the penultimate second from last lap but one!"