Thanks for reaching out about this. Emma will add each member from your list to the group you assign it to, regardless of if it already exists in Emma. It will not be added to a particular group more than once, though. Emma will not ignore contacts on your list that already exist in Emma, but it will de-dupe them if they already exist in the particular group you're adding the list to. Does that make sense? Let me know if you have any additional questions about this! Happy to help.