Look at each row. A properly configured FULL-range display shows every small patch clearly separated from its neighbors. A LIMITED-range display will merge the first few patches together (as solid black) and the last few (as solid white).
Near-black (RGB 0–31)
Near-white (RGB 224–255)
Continuous ramp (0 → 255)
Tip: Windows HDMI often ships with Limited Range by default. In NVIDIA Control Panel > Resolutions > Output dynamic range set to "Full". On AMD, Radeon Settings > Display > Color Range = Full. On game consoles the label is "RGB Range" or "HDMI Black Level".