Rather I refer 6 people or 20 people in a day I still only receive 1 - 3 (50 point) Referral Bonus Registrations. I use to get credit for a lot more of my referrals but I guess somehow my account was limited to how many referrals I can receive credit for.
There are no referral limits for members on MintVine. Keep in mind your first referral points will appear after their account has gotten approved points.