The 10 grams of protein that most of us get from cereal and milk at breakfast, he added, is not enough to get the bodyâs muscle-building machinery working at full throttle. For that, we would need to eat about 25 to 30 grams of protein, the amount in a three-egg cheese omelet.
For example, the prefix kilo means times a thousand or one thousand of the units in question. So  kilometre means one thousand metres and kilogrammeans one thousand grams.
K stands for 1000 (Kilo) in term of money.It is standard SI prefix. It is convenient to write instead of writing 3 continuous zero we write only one prefix K. it is also general convention people generally used to represent million to M thousand to k etc, and also meaning is changed as the context is changed.