The listener has the option to determine the length of an SSP listening session by adjusting the slider visible after the volume test. The 30 minute default can be adjusted up or down, to a maximum of one hour and minimum of 1 minute.
To adjust the slider, hold your finger on the bubble until it changes to a time indicator and move it to the desired point along the line. The slider can adjust both ends of the listening session. See the image below for what the two bubbles look like on the app: