Venues publish imbalance data in the minutes before an auction so liquidity providers can step in against the excess. The feed typically carries paired quantity, imbalance quantity, imbalance side and a reference price.
It is genuine tradable information, which is why paying for it is a real edge for closing-auction strategies and why the feed itself is a licensed product.
Example: at 15:50 the feed shows 1.4 million paired, 620,000 sell imbalance, near price 31.20. A desk sells nothing and instead bids for 300,000 at 31.05, expecting the imbalance to push the cross down. The close prints 31.08 and they own stock at a discount to the 15:50 reference. If the imbalance had flipped to the buy side, they would have been leaning the wrong way.
Related: closing-auction, opening-auction, indicative-price, order-book-imbalance