I will try to see him again.
It appears to be normal practice to not include the first iteration Phil. This doesn't prevent your point from becoming pertinent at the next iteration to 16. With rounding it would be:
1 serve : 1 tsp
2 : 2
4 : 3
8 : 5
This is how I interpreted his answers anyway. There is a slight language barrier issue although his English is quite good. It was quite busy where he was working, and I was in a hurry as well, so I didn't have the time to really press him. He may have meant to only reduce the increment by 20 % or it is even possible that he misunderstood my question about every instance of doubling and just did the math in his head for the amount I asked about. He did think for a second or so before answering.
So that would be either (with rounding)
1 serve : 1 tsp
2 : 2
4 : 3.5
8 : 6.5
or
1 serve : 1 tsp
2 : 2
8 : 6.5
10 : 8
My initial interpretation of his answers though, was consistent with my discussion with Ian, although he did say to use a factor of between 1.5 and 1.8 depending on previously mentioned criteria.
I think it is important to remember LC's recommended method to be used for final adjustments. If I was to make a batch for 32 or 40 serves at a conversion factor of X 1.5 and taste that it was OK, I'd leave it alone. If it was clearly under-spiced I'd use his method of adjustment.
As I've said, this is new ground for me, having only done it once before and I cannot remember exactly what I did last time (4 years ago) although I'm positive I did use the 1.5 reduction factor because of my target consumption group. I now wish I'd kept notes.
Posted at the same time as you LC. I think you are raising the most important point here. Increasing portion quantities is not directly just multiplying anything by a number. Increasing from 1 to 2 serves will be different to increasing from 10 to 20, and this will again be different to increasing from 100 to 200. The chef must know how to make those adjustments.