You can add multiple aliases

You don't add the additional alternate addresses in column 4, you just keep adding columns for each additional addresses. The example above does show this, but it isn't obvious at first since they mixed in the example of the IM address. But here's an example with more addresses:primary@domain.com,Firstname,Lastname,alt:add1@domain.com,alt:add2@domain.com,alt:add3@domain.com,alt:add4@domain.com