Is Ruby real, or is it just a dream?

I've been reading some of the other theories about this movie. How they say she's not real and what so ever.
But! There is some more details that can make this theory real.

Have you been noticed, that in the first two "dreams" Calvin has about Ruby, he is wearing the same clothes? Oh, you have?..
Well, have you also been noticing that these are the some clothes he is wearing the first time he falls asleep at the desk, and the next day he is meeting Ruby for the first time? If you do not think this is a coincidence, how about this;
That Last time Calvin sees Ruby, he is still wearing the same clothes as the last mentioned moments. And he also falls asleep this time, and when he wakes up, Ruby is gone. And if you do not think that THIS is a strange Coincidence, how about this; where is falling asleep? At the desk.

So, how do we know for sure, that all of this isn't a dream? He is falling asleep and wakes up at the same spot, and is wearing the same clothes.
How about that.