The Bubble criterion determines the size of the circles around the elements. You can drag the yellow bars to zoom in on the chart.
In the following image, the X axis is set as a Date attribute: Available on market and the Y axis is set as an estimate for Resolution. You can see how the Target Value, which is the resolution value to reach or exceed, changes over time. You can also see the resolution value of Competitor Technology X, and how the resolution value for Our Technology X and Our Technology Y changes over time. Some technologies in the chart have been implemented according to the status icon, while others are marked as new. The connector is set to Parent Folder, which is the common denominator for all of the elements.