Supervising Learner on 18t Horsebox

That’s very interesting Rog about the exemptions, so although I’m only a Supervisor and not Qualified Instructor, then provided the box doesn’t have a horse in it then the learner would select ‘Out of Scope’ on the Driver’s card and I wouldn’t need to use my card in slot 2.
If we are transporting a horse(s) then both cards would need to be used?
One other question, if the Box was loaded, do I apply ‘Double Manning’ rules whilst acting as a Supervisor?