you signed up for an annual plan (at a discounted monthly price in exchange for a one year commitment) similar to a car or appartment lease. though instead of making the lease unbreakable (like appartment and car leases), adobe allows you to terminate the lease early for 1/2 the cost of the remaining months.
eg, if you want to use adobe cc programs for less than ~7 months, you should sign up for a monthly plan. the cost per month is greater than the annual plan, but there's no lease/termination penalty. from usage more than ~7 months it's more economical to pay the lower monthly, terminate early and pay the penalty.