Hello @DANNE FRANKS,
My name is Henry and I am happy to assist with your inquiry, and appreciate you contacting LastPass Support!
If I understand correctly, if you imported all your passwords into a second account and then you are going to import your passwords from that second account into your main one, then yes you are going to be duplicating some passwords. During the Import process, LastPass will let you know if there are duplicates so you can exclude them.
Thank you,
Henry | Customer Care