To Set Up the Balloon Size (AutoCAD Mechanical Toolset)

At the Command prompt, enter AMOPTIONS.
In the Options dialog box, click the AM:Standards tab.
In the Standard Elements list, double-click Balloon. The BOM Settings dialog box appears.
In the Default style section, click . The Balloon Settings dialog box appears.
In the Balloon size factor box, specify how much larger than the balloon text the balloon must be.
Note: The balloon size is determined by multiplying the balloon text height with the size factor.
Click OK until all dialog boxes close.