If there is any truth to this timeline, then presumably it just means an additional 2 weeks of RL training on Astra.

"Twice as capable in mathematics" just means they found some problems that Astra couldn't solve, or make progress on (who knows how they chose to define "capable", or "twice as" for that matter), then put those 2 weeks of training in to focus on those gaps.

At this point, focused on their IPO, the best way to interpret OpenAI press releases is "what is the least this can mean, without being an actual lie". They are not shy - if there was a more impressive claim they could make, they would have made it.