Line 18 of Worksheet 2 from IRS Pub 501 would include any "other" expenses you paid for the person you supported that were not included in Lines 14, 15, 16 or 17 of the Worksheet.
Most expenses will fit into the four categories given in Lines 14-17; however, if you have an expense that does not seem to fit one of those categories, you would include it on Line 18.
