Deadline cards not shown

Hi! I have a set with 1800 cards ish and set the deadline for 10 days(just to try) and it says i only havent seen 180 ish
I have been doing this set for some days now but i am sure i have not seen 900 diff cards yet ?
It is for an important test and i am afraid i wont be able to see all of them before (it is over a month to my test but set the deadline in 10 days so i can recap and master them for 20)
Please help