How much milk? That question has only a few possible answers, and none of them are an accurate measurement. If someone replied "25ml" to me I'd assume they were a sarcastic twat.

a tiny bit - still dark, just enough milk to take the bitterness away
not much - a bit more than above, enough to turn the colour a little lighter while keeping the tea strong
normal - not too milky, but not too dark either, in the middle
milky - normal with an extra splash
really milky - ratio of around 1:3, for morons who don't like tea but do like warm milky water