I’ve not had a sample pack before so can’t comment on whats wrote there. I use 1/3rd of a teaspoon of a flavour per 90g of Huel with 450ml of water. It’s recommended to use more flavour when using U/U Huel because that doesn’t have a sweetener in it so will need more flavour to mask the earthy taste of U/U.
When using the flavourings from a full 150g pouch, it is recommended to use more flavouring for UU than for vanilla to get the full effect. As the sample pack of flavouring is of a specific size, the quantity of Huel must therefore be adjusted (for this sample meal only) to replicate the effect.
Once you have tried the flavouring, you can order a full pack of the one(s) you like and use whatever amount suits you.