It
could come off as desperate. If you really contributed meaningfully to the project, you would be listed as an author and not as an acknowledgment (depending on the PI and how willing they are in listing students as an author, of course...if you have a PI that's a dick and doesn't give you authorship even if you contributed significantly, that sucks and I'm sorry). The fact that the OP was listed as an acknowledgment suggests that he/she did not contribute meaningfully to the project;
why bring attention to that? You're missing the point that an acknowledgment is really worth nothing. It doesn't matter whether you're acknowledged or not, so there's really no point in mentioning it on AMCAS.
Just discuss the project and your extent of involvement in the project.
Being able to discuss the project in an intelligent manner is far, far more important (and useful) than listing an acknowledgment.
Disclaimer: I'm not an adcom, so if
LizzyM or someone pops in and says that they
do give brownie points for an acknowledgment, feel free to follow their advice.