I think on my 6.8" WQHD+ 3200 x 1440 phone screen (70.5mm width), an actual 5x5 pixel square might be the size of a period → .

Doing the math, 70.5mm / 1440px = 0.05mm per pixel, x5 = 0.25mm wide. Just a guess though, I'm not exactly sure how big a period is without a microscope.