Book health looks for things that stop Renewal Book working well: policies with no renewal date, terms that end the day they start, carriers with no rate, clients you can't reach, and more. Fix first comes first.
Duplicate clients (similar names with the same address, email or phone) and duplicate carriers can be merged. The duplicate's records move over and it goes to Recently deleted; restoring it moves everything back.
Not really the same? Choose Not the same and that pair isn't suggested again. A line of business we don't recognise can be kept as your own with Leave as is.