The short explanation
The first figure counts the main channels, the second counts subwoofers. 2.0 is stereo, 5.1 is five speakers plus a sub, 7.1 adds two more. Atmos setups add a third figure for height speakers: 5.1.2 means five, one sub, two overhead.
Where you run into it
Capability data carries the channel count, and a source respects it. If the chain advertises 2.0, you get stereo — even with a full surround system connected and configured.
It is one of the most visible EDID symptoms, because the receiver's own display tells you what it received. A receiver showing stereo on a 5.1 soundtrack is a capability problem, not a decoding one.
How the DR HDMI 8K handles it
Every predefined EDID table in the DR HDMI 8K's library (numbers 11 to 100) exists in 7.1, 5.1 and 2.0 variants — that is why there are 90 of them. If a system is stuck in stereo, switching to the 7.1 variant of the same video format is a one-click test that isolates the audio capability from everything else.
Want to test your own HDMI chain?
The DR HDMI 8K is sold through the HDFury.eu web shop.