Use the Bubble Chart Properties tab to set specific bubble chart options.
To set bubble chart properties:
Select Chart, then Properties.
The Properties dialog box is displayed.
Modify the properties as desired and click OK.
Show negative bubble—Display bubbles with negative values. These type of values are derived from their real absolute value, and the real negative value is depicted in the data label (although based on the positive value).
Show zero bubbles—Display bubbles with zero size values as a visual reference.
Max bubble size (%)—Set the maximum size of the bubble in the grid area. This size is measured as a percentage value. The default value is 25%.