Am I right in thinking that if no descriptor applies more than half the time, you get points for the one that applies the most?
No, you wouldn't get points at all.
I think it's great that you are trying to give a clear account of the variability of your situation, but it sounds a little confusing to someone who doesn't know you. From what you've written, it sounds like you need to say that you need supervision and assistance on the five days you are able to try and prepare a basic meal.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems
OK yeah thank you. I realised that it's 2 points either way whether it's supervision or assistance, so there's probably not that much value in being pedantic over which days it is supervision vs assistance, so I'll just explain i need them most days.