How is the limit of direct referrals calculated?

First of all, you can only have direct referrals after you meet these conditions:

• Been a member for at least 15 days
• Have made at least 100 clicks

After these conditions are met, the direct referral you can have will be based first on the following limit:

• Standard: 30
• Pioneer: 60
• Golden: 200
• Golden+Pioneer: 250
• Golden/Emerald: 300
• Golden/Sapphire: 300
• Golden/Platinum: 400
• Golden/Diamond: 400
• Golden/Ultimate: Unlimited

Depending on how many days you've been registered, all those days, minus the first 30, will count towards a limit increase.
This means that the older member you are, the more referrals you may have.
The amount will be based on your current membership/pack and the days you're registered (minus 30). This amount will vary and is explained below:

• Standard/Pioneer = Days-30 divided by 4
• Golden (without a pack) = Days-30 divided by 2
• Golden (with a pack) = Days-30

For example, if you have been registered for 330 days (which minus 30 gives 300 days):

• Standard= 30 + (300/4) = 105
• Golden = 200 + (300/2) = 350

If a user registers with your username he/she won't be your referral if you haven't met the 15 days/100 clicks condition or have reached the limit of allowed direct referrals.
You can always remove all direct referrals you don't want to make room for new ones.