The exclusion you refer to applies to disabled DC residents, not all DC residents.
According to Line 7a and 7b, Exclusions for DC residents in the Instructions for Schedule I:
Income not to exceed $10,000 is excludable in computing DC gross income for persons determined by the Social Security Administration to be totally and permanently disabled and who are receiving: Supplemental Security Income or Social Security Disability; or railroad retirement disability benefits; or federal or DC government disability benefits; and whose annual household adjusted gross income is less than $100,000.
You don't indicate that you have such a disability.
