If the target of the investigation had the capability to counter Divination, the related information Mazao managed to gather would be fragmented. She once described piecing together these broken shards of information as a "puzzle game." And, since it was a puzzle, it meant that with enough luck, it was possible to directly piece together the needed results.
Perhaps because there was no time limit last time, she couldn't give an accurate timeframe. But this time was different. For her, with the Broom Star Physique, missing the timing meant she would be unable to track the target, which was equivalent to "definitely being able to track the target within this period."