When you create a table of contents, you specify which paragraph styles, applied to your headings, should show up in the table of contents.
No other styles except the ones you specify (in Outline Numbering, or in other ways) should be included.
So if I create a style called DontIncludeMe and apply it to some text, that text shouldn't end up in the table of contents (TOC), right?
You would think so. BUT here's the thing.
If other styles that you apply are Linked With styles that are set to appear in the TOC, then those styles WILL APPEAR IN THE TOC even though you didn't tell them too. Take a look at the Linked With field above, in the style formatting window.
Now, this isn't necessarily bad, just to my mind unexpected. Just be sure that you know this is how it works, then use the Linled With feature appropriately. You can choose None if you don't want the style you're creating or using to show up in the TOC unexpectedly.