I am not sure what your question is, but perhaps this will help -
You will see the way to enter the subtraction for retired law enforcement officers only if the taxpayer is between 55 and 65 (65 or over, there is a larger exclusion that takes precedence).
Go to the Maryland interview in TurboTax, navigate to the screen entitled "Here's the income that Maryland handles differently" and look at subheading "Retirement". Click on "Retired Law Enforcement, Fire, or Rescue Pension" and enter the amount of your pension here.
Note that it will be limited to $15,000. It will appear on line "rr" on form 502SU.
The Hometown Heroes Act allows "retirement
income to qualify for the State pension exclusion if the individual is at least 55 years old and the
retirement income is attributable to employment as a law enforcement officer or
as fire, rescue, or emergency services personnel of the United States, the
State, or a local jurisdiction. Emergency services personnel include emergency
medical technicians and paramedics. " See http://www.bcfpers.org/2018/01/28/hometown-heroes-act/