At one point I was working at a printing shop. One time I was testing color calibration, running the same sheet through the printer multiple times, and these do

At one point I was working at a printing shop. One time I was testing color calibration, running the same sheet through the printer multiple times, and these dots became visible clearly. It was quite a head scratchier, we actually thought there's something wrong with our printer until I googled about these yellow dots.