Indexing - but already filled out

I am indexing the South African death records and several of the batches have the information already filled in. These are not in review because I chose them from the index button and it doesn't have the check boxes to say that I've reviewed all fields. What's happening here?

Also, I had checked out some batches of the Gibraltar Census the other day and didn't finish in one session. When I came back the next day, some of them were missing and a couple of them opened as a "shared batch". What does that mean and what happened there?

Thanks!