4K resolution
As noted above, DCI 4K is 40962160, while 4K UHD is 38402160, producing a slight difference in aspect ratio rather than a significant difference in resolution. Traditional displays, such as LCD or OLED, are 3840 pixels across the screen, with each pixel being 1/3840th of the screen width. They do not overlap—if they did, they would suffer reduced detail. The diameter of each pixel is basically 1/3840th of the screen width or 1/2160th of the screen height - either gives the same size pixel. That 38402160 works out to 8.3 megapixels, the official resolution of 4K UHD (and therefore Blu-ray UHD discs).
Graphics display resolution
This resolution, commonly referred to as 5K or 5K3K, has a 16:9 aspect ratio and 14,745,600 pixels. Although it is not established by any of the UHDTV standards, some manufacturers such as Dell have referred to it as UHD+. It is exactly double the pixel count of QHD (25601440) in both dimensions for a total of four times as many pixels, and is 33% larger than 4K UHD (38402160) in both dimensions for a total of 1. times as many pixels. The line count of 2880 is also the least common multiple of 480 and 576, the scanline count of NTSC and PAL, respectively. Such a resolution can vertically scale SD content to fit by natural numbers (6 for NTSC and 5 for PAL). Horizontal scaling of SD is always fractional (non-anamorphic: 5.33...5.47, anamorphic: 7.11...7.29).