Hi Tony
When you click on the dimension you will see in the "dimension text" box something like <MOD-DIA><DIM>. You can add your own text and symbols to this area and it will be displayed in the dimension in the drawing. If you CTRL select more than one dimension the added text, number will be added to all that you selected. Make sure you do not delete the text in the <> as this will not allow the sizes to update with changes.
Hope this helps
Regards
Trevor