When you add new editors to your team on an annual subscription, Figma will charge you a separate monthly subscription for those editors. You’ll have both an annual subscription, and a monthly subscription for any extra editors—we call this “co-terming”.
To simplify your account, you can convert your monthly seats to an annual subscription. Figma will charge you a pro-rated fee, which covers those editor seats for the rest of your annual billing period. More info here: