Where is the hard option in Zombie Mode?

Where is the hard option?In you character details in game it says:

hard normal easy
unearth 0 lets say 10 maybe 15
biohazard 0 here 12 14 i think

In the game room you select only normal and easy.WHERE IS THE HARD OPTION?????

(i am asking because its pretty impossible to reach 700000 points even with RPK-Gold!!!)