Paired And Unpaired Quantity

At an opening or closing auction, the exchange collects all buy and sell interest and finds a single clearing price that matches as much volume as possible. Whatever quantity can actually be matched — one buy order against one sell order at that price — is the paired quantity. If buy and sell interest aren't exactly equal at that price, which is the usual case, the side with more volume has leftover shares that found no counterparty; that leftover is the unpaired quantity, more commonly called the imbalance.

Exchanges publish paired and unpaired figures before the auction runs specifically so market participants can react: seeing a large unpaired buy imbalance tells other traders that the price is likely to be pulled up to attract more sell interest, and imbalance-only order types exist precisely to let traders supply liquidity against that leftover.

Worked example. At the close, 800,000 shares want to buy at the indicative price and 500,000 shares want to sell. Paired quantity is 500,000 shares (limited by the smaller side); unpaired quantity is 300,000 shares of unmatched buy interest. That 300,000-share imbalance is published to the market, and the exchange nudges the clearing price up to attract additional sellers before the final cross.