Hi Stacey,
The number you are seeing in settings notifications for that app are an average for how many times that particular notification goes off. Hopefully that makes sense.
Not really sure why the number is there, but if I had to guess, maybe it makes it easier for you to identify why the app itself keeps giving you notifications so you can silence or customize just that part, and not to the entire app.
Example: If messages app keeps giving notifications, I could open it up and see that ~20 per day come from one person, I could silence just that one person or change their notification sound so i know it is from them and don't need to look right away etc...
Scott