Hi! That's also my first gamejam and i also tried to make horror game!
Your jumpscare maybe not very scary on its own, but how you timed everything and placed it in very unexpected place, when you just feel that you have control and nothing will happen when text on-scree, that's what made it so great! And image actually wasn't somewhat scary, but sound and timing was! Also, because i felt like something will jump at me at sometime, i was paranoid, so it turned out as it is!
I didn't ended up ready whole text because when i was deciding to press or not PrSn button it striked me, soo yea. If you have it i would like to read :).