When considering investments, it is important to understand the aggregate size in board lots of the most recent ask to sell a particular security. This term refers to the total number of shares being offered by sellers at the current asking price. Essentially, it represents the available supply of the security in the market. As a knowledgeable investor, being aware of this information can help you make more informed decisions when buying and selling securities. Remember, the aggregate size in board lots is just one aspect to consider when evaluating potential investments.