That's the short answer. And carbs, to some extent (skimmed milk is surprisingly high in carbs).
There are a few of us around here who do SS and also have a small quantity of skimmed milk each day just so that we can have a proper cup of tea once in a while. The general consensus is that it doesn't do too much harm - might make a difference to your weight loss of about a quarter to half a pound a week - but there's a theoretical chance it might make you hungry (that'll be the carbs). It doesn't make me hungry (but your mileage may vary) and of course, if you were doing SS+ you could have 200ml of skimmed milk a day anyway.
Long and the short of it - if you want the occasional cup of tea with milk, I don't think it does too much harm. Don't go mad though, cos all calories add up!
I used to do it occasionally. The lowest carb milk is the fattiest too, full fat milk has the lowest carbs but the fat content is huge. Ok on Atkins. Skim milk has higher carbs but also higher calcium too. All swings and roundabouts!
but dont the tetras have same calories as sachet ones? and if i was having 4 of them a day id be having more milk than i am on just one a day - didnt realise skimmed milk was high in carbs, will only have it occasionally thanks!