Checking Use Count
Flash CS4 Tutorial
How to Display Number of Times a Library Object is Used in a Flash Project
Use Count is a valuable tool to see if a Library asset is being used in your document. Each time an object is added to the stage, it's Use Count increments by one. Unfortunately, Library assets that are added with ActionScript (Export for ActionScript) still register with a Use Count of zero.
Open a new Flash document and select the first frame of the default layer.
Draw an oval shape with the Oval tool (o key) on the stage.
Select the oval and convert it to a Movie Symbol by pressing F8.
Open the Library (Window > Library (Cmd/L (PC - Ctrl/L)).
Your symbol is listed. Scoll the Library panel to the right to view the Use Count column. It shows one use of the symbol.
Drag two more instances of the oval from the Library to the stage.
The Use Count now reads three.
Beware of File Bloating
Unused Button Symbols or Movie Symbols in Library don't always increase your swf file size. However, if you create a symbol and check Export for ActionScript when creating the symbol, the swf file size will increase even if the symbol isn't used. For more information, see topics, Export Library Button Symbol for ActionScript and Export Library Movie Symbol for ActionScript.