You must do one of the following:
1. Change your line spacing to match the line numbering and then adhere
exactly to it.
2. Modify the spacing of the line numbering itself.
With regard to (1) and (2), you can find out the line spacing of the
numbering using View | Header and Footer and then checking the formatting of
the text in the text box that provides the numbering. If the line spacing of
the line numbering is set to an Exact amount, you can set your body text
style to that amount. If it is Single, then it is dependent on the font type
and size. If this is different from what you're using in your document, then
you can modify the style being used for one or the other. If you are
required to have a certain number of lines per page, you may not be allowed
to change the line numbering.
3. Use Word's built-in line numbering feature instead. This is really the
only viable option if you have, say, single-spaced material interspersed
with double-spaced, or some text in a different font size. Find this feature
on the Layout tab of Page Setup. (You can then view | Header and Footer and
delete the text box or frame containing the line numbers.)
