I also self-reported the wrong GPA. I under-listed it by a half-point because there didn't seem to be enough space for the second decimal. I think if you go to mba.com there's a way to change it, or at least set it so that it doesn't report your self-reported gpa. The first couple schools I reported my GMAT score to had the self-reported gpa, and somehow I removed it for the ones I sent later.
Regardless, when you fill out the business school application you have to give your undergrad gpa. I'm sure they don't even bother looking at the self-reported GMAT one. I didn't mention it to any of the schools I applied to and none of them seem to have cared.