Question about measuring/black plunger in syringe

[Philly Grappler]

I have always used the very bottom of the black plungner inside the syringe as the measuring point when drawing from a vial, however, in the middle of the black plunger is a line. Have I been measuring wrong all this time? Is the line there in the middle of the plunger for the point of measure? What part of the plunger is used to measure an accurate dose?

[Mr.Rose]

You measure to the top of the black plunger.

[forrest_and_trees]

Nice illustration!

[Philly Grappler]

Thanks for the reply. I wonder why the plungers have that line through the middle of the plunger.