Doc-O-Matic assigns topic IDs using the file name and heading texts as topic IDs. If the heading text or the file name is a symbol name Doc-O-Matic associates the comments with the respective symbol. 

Alternatively you can insert the HTML topic identifier. However you can only insert the HTML Topic Identifier once in a HTML file. The default HTML Topic Identifier is:

THE_SYMBOL_ID is the topic ID of the symbol described in this file. In the following example, the comment instructs Doc-O-Matic to associate the comment with a function named Control::Initialize, which has one parameter of type Parent