If they registered w/ a 90 day subscription and then swapped it to 180 day, then it would put them at 450 days (90+180+180) at the 9 month mark (3 months + 6 months).
What you have is the case where your subscription won't lapse till the 1 year mark (6 months + 6 months) but when it does then you can reach the 540 day (possible rank 8 if available) mark before anyone else.