Comment by rt2016

Seems like it's documented here that there's a difference in referral bonus between the Basic and Pro accounts (https://www.dropbox.com/en/help/200). Maybe you had earned 6.5GB in referrals on your Pro account, which has now been reduced by 3.25GB. It's frustrating that they're taking away the benefits you earned while paying for the Pro account, but it's not unusual.