What I'm seeing is a confluence of things. One is duplicate books, I'll sometimes have up to 4 duplicates of the same book show up in Readwise. I think part of this is them coming from different sources (one from iBooks, one from API, one from supplemental, etc). Sometimes things highlighted with hypothesis and then also on Pocket come in as separate sources
Side note what's the 'saved_supp' source? It's sometimes a duplicate of another 'supplemental' source