Maryland military retirement pay income tax deduction maximum

According to the Maryland 2018 tax code, the maximum amount of military retirement income that can be subtracted from income is $15,000 for taxpayers over age 55 on Form 502SU. However, Turbo Tax limited this subtraction to $8586 with an explanation that it is the Maximum Allowed (after Social Security/Railroad Retirement). This is not correct. How can we fix this Turbo Tax error?