@Art Vis completely correct that it is about screen resolution. Here are some examples. I am basing this on a wide screen monitor (16:9) as it can be considered to be a 3:4:5 right triangle.   A 30" monitor with 2K resolution: 30" diagonal = 24" horizontal  24"/2000 pixels = 0.012"/pixel = 12 mils = 83 pixels/inch.  So the minimum individual pixel will be 12 mil.  Anything with a line weight of 12 mils will show as 12 mil. Depending on the display driver algorithm, line thicknesse