Hmmm! That's very odd and I'm sorry to hear you're having trouble!
I'm not sure what could be happening -- it could be that .zip/.rar files tend to be smaller than what's actually inside? So, what Itchio says the game is, isn't the true size simply because it's in a compressed format.
The game doesn't take much to run, but it is heavy on images and text, which simply take up space. (Plus, I haven't optimized the game as best I could yet simply because this isn't the finished version yet!)
I'm not an expert on anything computers at all (I'm mostly a comic artist who does game dev on the side) so this is the best I could come up with.
My suggest would be to play the game quickly and then just delete it. It takes less than 30 minutes to get through the game on the current build, so it won't take up much of your time. I'll see what I can do about lowering the file size in future versions as well. Thanks for your comment!