https://www.titan.com/articles/what-is-an-at-the-market-offering

ABC, nice job on details. The above link will take you to an article by Titan Securities which explains it  simply and well.  There is no negotiated price, the agent sells "at the market" on the day that is chosen. Depending on the overall volume that day, they may sell none, or a bunch. In Poet's case, even on a pretty busy trading day, I doubt you'd see more than 25,000 shares offered, for fear of depression the price. Theoretically, we will not know when the ATM is "tapped."

The sales can be timed to coincide with such events which generate high volume and a price increase.