Payment for year-long FB Plus

Hi, I need help interpreting the info about the year-long FB Plus pass I purchased for this year. On Dec. 19, 2022, I purchased the $79.99 eGift Card for one year of FB Plus, at a discounted price of $59.99.

I'm just having trouble wrapping my head around how my purchase is now applying to my subscription. I see I wasn't charged anything for the Jan. 2023 monthly fee, but I also see that my credit has been reduced, which is confusing to me. I also thought I purchased a year of FB Plus, so why am I getting monthly billings--shouldn't it be annual?

Thanks in advance for your help! I love the customer support here :)