Teh C is the tea with evaporated milk, the C is for Carnation, the old milk brand. Because the milk is unsweetened, you have more control here. The sugar is added on the side, so kurang manis actually makes a real dent, unlike condensed milk where the sweet is baked in.
Standard teh C is about 130 calories, so a little lighter than teh ais. Not a huge difference, but if you drink a few a day it adds up in your favour. Order it kosong, just tea and evaporated milk with no sugar, and you are down around 70.