With no quote how are we to know who, or what, you are agreeing with?
No wonder you’re having so much trouble with the concept of oil in an engine.
I have no trouble with "the concept of oil in a engine"
I own and maintain a Lycoming O-360 and a Lycoming IO-360. When I change the oil and filter on each of these engines I add 7 quarts. After engine run for leak check they both show about 6.5 quarts on the dipstick. They are both indicating that there is 6.5 quarts of oil in the sump. There is no indication anywhere that there is 7 quarts of oil in the engine but I know there is because I poured it in and it didn't come out.
Both engines use factory marked dipsticks and I believe their indications are normal. As you say it isn't rocket science. A correctly calibrated dipstick on a Lycoming O-360 or IO-360 shows the oil quantity in the sump.
Ha Ha! I’ve typed something similar several times and then deleted it..... Glad I’m not the only one that thinks it may be possible some are overthinking this. The 185 I flew on floats had 2 X’s, low and high. Keep it between the X’s and all is good. Longer flight? A little closer to the top X......
Who marked it?
I take it you were flying somebody else’s airplane that somebody else maintained?