Totally closed, is 40gr. The first visible line is 50, etc.
The only way to know which is correct, is to weigh the powder charges thrown by both.
Lee Valley tools has an inexpensive digital scale for way under $20.00. It weighs in grains,
ounces, grams - etc. I keep one in my shooting box - not sure why, now that I think about it.
Different powder makes as well as different granulations 'throw" different weights from the same measure.
Use the adjustments to change loads until you find a load that works best for you, THEN make a single non-
adjustable measure to 'throw" that amount. No scale needed.
I make powder measures out of brass tubing from model airplane/car stores as well as from ctg. cases I pick up at the range.
I drill out the flash hole for a screw-eye, then turn the end off to a rounded shape on the lathe. An electric drill held in a bench
vise will also work, but 1/2" drill will be needed for most brass that will throw over 25gr. 3F.
With the tubing, which has a .015" wall and successive sizing that each larger size just slide fits into the next size. for those, I make
a soft-wood plug, glue it in with CA and drill a hole across for a string. Several of these measures are like that. I have one that throws
35gr. and it's only 5/16"" in diameter(bottom right), along with several throwing from 62gr. 3F to 165gr. 2F. top row left and top row right.