I am trying to understand how the billing process works for "Intuit QuickBooks Payroll Annual Subscription One Employee Included Enhanced".

Last month my credit card was billed $509.55 for "Intuit QuickBooks Payroll Annual Subscription One Employee Included (Billed Annually)", but I am already signed up for Monthly Per Employee where I'm paying $12.90/month for payroll service based on the number of employees. 

Why am I being billed annually on top of the per-month pricing?