Only you and the PD see the score. It's supposed to give you an idea of where your medical knowledge is standing. If you don't do well, programs should have a remediation program to help you fill in the knowledge gap. It also gives you breakdown of what part of GI you have weaknesses in. I used that to guide where I spent more time reading up. You are not supposed to study for ITE per se. Not sure how it correlates to actual boards, and if there is data on that, but it's pretty similar to real boards so I think it should. So it "matters" only for the above purposes.
An important question is are the actual GI boards any good. Seemed to be filled with many pedantic and esoteric things.