The input for live streams is the length of your broadcast in minutes. It measures how long your live stream is from start to finish. Live stream delivery refers to how many minutes were streamed in total to each viewer of your live broadcast.
For example, if you have a 10 minute live broadcast to 100 viewers, you would use 10 minutes of input time, and 1,000 minutes of delivery, assuming everyone watched your entire broadcast while streaming live.