Once you have added a concert to your archive, you have the ability to select which bands you saw and which you didn't. If you didn't see a band, it won't be included in your stats.
To select the bands you saw, click the button that says "Select the bands you saw" at the top of the Band Line-Up section.
When you click that, you'll see check marks appear next to each of the bands in the Line-up. Uncheck the box for each of the bands you didn't see.
When you are finished, click the 'Done' button.