Hi Millie,
If you do 4 packs + Veg or 3 packs + the protein meal the weight loss is virtually the same simply because the only difference is the 100g of protein so they have got it worked out that your getting the same cals either way.
The only difference is that having the protein meal is lower in carbs than having the 4th pack which I prefer as I am finding it a struggle staying in ketosis on 4 packs but fine on 3 plus the meal, but everyone is different so it's all about finding what suits you x