What is a referral?
A referral is someone who uses your unique referral link to create a Dropbox account. He also has to log in using the Desktop Application in order for Dropbox to reward you with 500 MB of extra storage.
Why do you say up to 16 GB of extra storage?
Dropbox rewards your with 500 MB for each referral, with a maximum of 16 GB. In case you already have some referrals in your account, some of the 32 extra referrals will not provide you with an extra 500 MB of storage. What we can guarantee, is that your free account will have at least 2 GB + 16 GB = 18 GB of storage after using our service :-)