I know this is probably gonna sound a bit silly but how much potato can i have on an original day as a HEX B, want to do roasties but not sure if this is the same as 227g baking potato but without the skin?
It's because of the fibre.
Unofficially, and don't tell anyone I said so (!) - I do sometimes use peeled pots on a red day and call it a heb, but you shouldn't really.