The Ask price is the minimum price at which a seller is willing to sell his/her crypto holdings. Sellers when putting a limit sell order mention a price at which they want to sell a particular cryptocurrency for a specific price. Once they place a sell limit order, the order is moved to the ask order book along with other ask orders. Ask order book usually has a higher price as compared to bid order book.
The first column in the screenshot i.e Price shows the price in the desired cryptocurrency. The second column i.e Volume shows the total volume a seller is willing to sell for the price. The third column i.e Total BTC shows the price per unit * volume of the desired crypto currency. In this screenshot, the price set by a seller in the top most order is 0.4 BTC per 1 unit of ETH. The seller is willing to sell 0.4 ETH for a total price of 0.16 BTC as mentioned in the third column.