Any chance you pulled a Rip Van Winkle and slept longer than expected?
Seriously, though, I've never been clear on the numbering system for definition upgrades myself, and haven't recognized a clear pattern as to when they advance to whatever-0. If I go from something-3 to something-5, I can assume I was offline longer than usual, or maybe there were two almost back-to-back that I picked up together.
