Just tried it & it subscribed me to two lists instead of just the chosen one

I’m using Mailpoet and selected ‘My First List’ in the campaign settings. But when I got the confirmation email, it said I was subscribed to ‘WordPress Users, My First List’. I clicked the confirmation link and saw in Mailpoet that I had in fact been subscribed to both of those lists – even though it only should have been just to ‘My First List’. Is there any way to fix this?