What is what does bottom of the hour mean?

"Bottom of the hour" refers to the exact half-hour mark on the clock, such as 12:30 or 1:30. It is commonly used in broadcasting and scheduling to indicate the specific time when a show or event will begin, especially when it is scheduled to start on the hour or on the half-hour. For example, a news program might be scheduled to begin at the "bottom of the hour" of every hour, meaning that it starts at 30 minutes past the hour.