This is just a small bug with novels being in more than one reading list at once, i am not sure how it is even happening. This also creates a situation where a affected novel shows more than one icon. Its just a mere annoyance since they are easy to remove again.
Actually I want a feature like this where the same novel can be placed in multiple reading list......
I am not even sure how it did happen, seems quite random and rare, i first thought it did only happen if they were in that list before, but that was wrong when a novel did appear in a list it never was in so idk anymore. https://imgur.com/Pm2npCt Also, it doenst show up in multiple lists on the novel page.
Got the same problem not a while ago, idk how this happens, i did not touch the novel. Just notice that on the main page it have two pins for lists. Sadly don't have any screenshots of that