I don't think you're understanding how the feature works.
As I understand it, the ones on the bottom line are your most recently used reactions.
When you click on the reaction icon, you have a sort of "menu" across the top of the box underneath Search. The first is "Smileys and emoticons", the second (the hand) is "People and body", the cat is "Animals and nature" and so on. If you click on one of the top categories, you'll get completely different display of reactions in the box below it.
I'm guessing you likely clicked on reactions you already saw on posts to agree (that's why they're showing up on your bottom line) but you aren't clicking on the right icon on the second line to see all the choices.