Hi! Thanks for reaching out. Understanding audience totals after adding addresses or importing a list can be a bit confusing. Most often, the audience number doesn't change because the address actually already exist within your audience. It is possible for that address to exist in the Active, Error, or Optout status.
The quickest way to verify that the members are already in your account is to type their email address in the quick search bar near the upper right of your audience page.
From there you will want to check the Active, Error, and Opt out tabs to see if the address is already in your account. You can move them from Error to Active by following the instructions here. If the address is in optout, the customer will need to signup again through your signup form in order to be added back to your active list.
Please let us know if there is anything else we can assist you with.