Fantastic! You saw that the position of the object in the beginning was at \(0\), it went up to \(20\) and then returned to \(0\).
Look at the animation alongside to understand how to interpret the graph. The figure initially moves to the right, stops once it reaches a maximum displacement of \(20 \, \mathrm{m}\) and then turns around and walks back. As it walks back, the displacement keeps decreasing, until it reaches a value of \(0\), when the figure returns to the original position.

Such graphs are called position-time graphs because they plot the position of an object as a function of time.