If you are seeing a lot of mentions that are unrelated to your rule set, it might be a result of one of the keywords pulling in irrelevant data.
In order to get rid of the mentions, you can delete them under the Mentions tab.
Once you've deleted them, you can add an exclusion rule to the Monitor by going to Edit Monitor.
Once you're on the Edit Monitor page, you can add the exclusion to include whatever spam words that might have been coming in. For example, many users like to exclude profanities, inappropriate content, and other unrelated terms.
Once you've made the changes, you can see a preview of what might be pulled by clicking the preview button. Also, when you save the monitor, it will give you an estimate of how many mentions will be pulled in.