That figure lines up with the non-moving indicator on le lens barrel such that the 18 is still to the left of the indicator, so it is pointing to show that position is 18 mm.
The do the same with the AF-MF switch and the Stabilizer switch.
Think that is just the marker to show where 18mm on the dial is. When you turn your zoom all the way over to wide, it stops just beneath that "flag" - as you call it