How do I read the Slots filled chart?

Slots filled is a step chart that shows how the lineup filled up over time. The line goes up each time a player joins and goes down when a player leaves, so you can see how fast the game filled and when people dropped out. The right end of the chart matches the current joined count, for example 4/18. Both organizers and players see this chart on the Overview tab. History starts from the release of this feature, so older games may show only what happened after that.