score:6
Airpoints practices what FlyerTalkers refer to as a soft landing in that failing to requalify for a status tier only drops you to a tier below, rather than losing all status (a hard landing).
Your Gold status is valid for 12 months from the time you earned it, which is to say November 2017. Even if you did not earn a single status point after attaining Gold, after your anniversary you would drop down to Silver status.
Your anniversary dates are maintained, however, so to retain Silver, you will be starting from zero as of November 2017, with 12 months to earn 405 status points to retain Silver.