According to Retro old post " 1500 points - referrals " thats how many marks should using a referral give. However i just used a referral i had and gained no marks. Cannot duplicate this bug again as i have no more referrals to use.
EDIT: Confirmed. Another character that had 9k marks just used a referral and still has 9k marks
EDIT2: By using referral i mean it was used to get 20 days of premium time+1h SB