Unearned rent is a liability account that recognizes the rent money Goodwell has received for months that haven't happened yet (rent money hasn't been earned). After each month passes, Goodwill will debit (reduce) unearned rent by $2,200 and credit (increase) rent revenue by 2,200.
On December 31, the company will have reduced unearned rent for 3 months (October, November, December). This will have the following effect on the account balance:
11,000 - (2,200 * 3) = 11,000 - 6600 = 4,400
The adjusted Unearned Rent balance at the end of December will be
$4,400