I seem to have found a workaround for this issue. You can number the lines on forms by adding a column to the form template and using the numbering function in MS Word. It should show "1." in the template. When a form is generated, the subsequent lines will be numbered as well. You do not need to include the <<TableStartlines>> field code in this column. You can include it in the next column and it still works fine.
Please comment if anyone finds a better option.