When you add a Query to your Topic you are now having our crawler search using two different sets of criteria. Once you add the extra query you will get more results relating to your Topic.
To add a Query to your Topic, click your Topic at the top of the screen. Once the menu drops down, click "Edit TOPIC". At the bottom of the pop-up you'll see "Add Query", click there. It will bring up the Guided Topic Builder (you can choose to use the Advanced as well) to add another Query to your Topic.
NOTE: You need to have at least one initial query started before you can start adding additional ones. Click here to learn how to create your first Topic!