The email that came from (ISC)2 announcing AMF and policy changes included this statement : -
Starting January 23, 2019, members have until June 30, 2019 to pay any outstanding AMFs and the option to pay ahead for the remainder of their three-year membership cycle at the current rate for their certification.
Assuming your cycle started last year, I suppose you're getting the option to pay the AMF for this year & next year in advance, at the rate of 85 USD.
@Lwhite Thank you for your inquiry. Shannon is correct in his statement regarding the updated AMF policy. If you would like me to look into your account and confirm exactly which years those payments are going to, please feel free to email me at firstname.lastname@example.org.