I don't understand your statement regarding the number of points (not more than 5-6 points) on a graph. When the Guideline and Standards states that you should not use more than 5 point symbols on a page (Section 3.2.2), it is referring to 5 different [u]types[/u] of point (solid circle, hollow circle, square, etc.) rather than the [u]number[/u] of points.
For example, when you are finding a line of best fit, there are numerous points along the line.
Perhaps I have misread your question. Would you please post a scan of the print illustration in order to clarify your question for me, and state a source for your information on 5-6 points?
Thanks! I'd be happy to answer your question if I had more information.