Why is it important to examine the unnumbered marks on a graduated cylinder before making a reading between the unnumbered lines?

I'm not sure of the question but I'll take a stab at it. It must be to avoid parallax; i.e, you want the eye level with the meniscus.

I will take another "stab" at this unclear question. First you would want to attend to the numbered marks to get the values related to the unnumbered marks. Then you can better estimate the values between these unnumbered marks.

I hope this helps a little more. Thanks for asking.