On my Shimano FC-6800 right crank arm, is that a QR code imprinted on it?
Its not uncommon for items to have serial numbers, to track them through the manufacturing process and out into the retail world.

QR codes can be read by cameras no matter which way around they are, compared to traditional 1-Dimension barcodes that can only be read in one direction, with some tolerances.

You're looking at a serial number for that item - if you still have your receipt it might be logged on there too.

If the QR code bothers you, you could remove it with light+gentle sanding or a solvent and touch up the surface afterward.