Yeah, that says what I have to do to reach that level (instead of going up a level), and how long the new level is valid.

It doesn't say whether the qualification is within calendar year or year-to-date, or, for that matter, a different timeframe - such as 18 months, same as SUMA miles validity perhaps?

Sure, you can logically infer that it probably goes by year-to-date calendar, but it's not stated anywhere.