For Spotify users on a "Free" plan, audio advertisements periodically play after songs. However, last.fm tracks them as their own scrobbles, especially through the mobile app. It's unclear whether this is was an oversight on last.fm's part. You may optionally erase scrobbled audio advertisements from your profile by navigating to your Library > Artists > "Shopify", then settings "delete artist from library". Do note that this will only erase advertisements you scrobbled in the past and may not prevent new ones from scrobbling through the last. Read more on Last.fm