The 27UD68-W has a maximum resolution of 3840 x 2160. That's over four times the resolution of a 1920 x 1080 (HD 1080) PC monitor, which is the most common resolution. 1920 x 1080 (HD 1080) is also found on this PC display.
A 3840 x 2160 graphics resolution is actually the best resolution amongst all medium monitors that were launched around the same time as the 27UD68-W.
A 640 x 350 graphics resolution is the worst resolution amongst similar types of PC screen.