A family of Microsoft word processing software products for creating web, email, and print documents.
To get the borders of the paragraphs containing the text in the Heading 1 style, you will need to fiddle with the paragraph indents.
For the following screen shot at 250% zoom, the left and right indents were set to 2 mm.
You might need to use Points or Picas as the unit of measure to obtain a finer adjustment.
To get the following alignment at 500% zoom, a left indent of 0.49 Pica was used