A mini-synthesis should update the case, not repeat the last fact. State what you learned, what it means for the hypothesis, and what you would investigate next.

The new information should change something: confidence in a hypothesis, priority of a branch, or the likely recommendation.

Practice making one-sentence syntheses after exhibits and calculations. If the sentence could have been said before the analysis, it is probably too generic. If useful, this guide on case interview insight generation gives more detail.