No you've got it right. But when your planting twenty vergess of Jersey Royals, more than egg boxes are needed! :-D Knock off one sprout, the spud panics and produces a lot more, hence more spuds. They were also graded by size the large one s planted first.
Jersey Royals should be planted in sand fertillised by Vraick, dried seaweed, that way they develop no lumps or a thick skin. The other ideal place are south facing Cotils, these are the steep valley sides, and I mean STEEP! The old way of ploughing used to throw a single furrow plough over the top and winch up. One old farmer had a Series 1 88 with a pto winch on the back speciffically for the job. The proper ones have a nutty tatse, and a cheese like texture NEVER fry! Always wash, never peel! Boil till just soft, best Jersey Butter and sea salt. We also used to glean for the ones to small to sell, naturally those are the best tasting!