Grey box on campanion says 31 thumbs up, but only 14 names

As the title says, I don’t get the names of all the people who have given me a thumbs up. I like to return the favor, usually after the ride as I can’t always find the person when riding. Also, people that follow me give me thumbs up sometimes when they are not in the same ride. Am I doing something wrong, or not understanding how the thumbs up works?

This might not be very helpful, but in my ZC on Android I can see the same number of names as ride-ons for my rides.