maximum stem extension line
 

hi guys..im using cinelli solido stem(120mm) and im curious about the wordings stamped beside the stem. It wrote there :-

120 0 19

Im not sure whether 19(in mm??) is the maximum extension line. I heard some articles said that it will eventually snapped off if we put beyond the maximum line. My stem setting is about 30mm above the headset.

There's usually a line scored around the stem to indicate the maximum extension.

120 is the extension length.

what? that means stem length=stem extension? if yse, what is that 19 means?

Here is the excerpt from the article :-

Stem Height: Start with the top of the stem about one inch below the top of the saddle. This should give you comfortable access to every hand position. As time goes by, think about lowering the stem as much as another inch (not all at once) to improve your aerodynamics. If your lower back or neck starts complaining, or if you notice you’ve stopped using the drops, go back up. Never put the stem so high that its maximum extension line shows, or it could be snapped off by your weight on the bar.