I agree that's a bit confusing and not very easy to explain
Hardware :
The preenfm3 has 3 setereo DACs that are wired to 6 audio jacks (mono).
There's a (mecanical) trick at the jack level, that redirects jack 1,3,5 to jacks 2,4,6 if you don't insert anything in 1,3,5.
In this case jacks 2,4,6 (or only one of them) become stereo.
That means that instead of 6 mono jack you can use 3 stereo jacks 2,4,6.
At the end you still have 6 mono outputs.
Firmware :
Each of the 6 pfm3 instruments have a Stereo output. Instruments can be routed to ANY of the jacks.
- only one jack 1,2,3,4,5,6. Instruments will be then converted to mono.
- regular usage is using 2 jacks : 12, 34 or 56 for stereo output.
Hope that makes sens.