It's certainly possible that the discrepancy you've mentioned may be brought up during the polygraph examination. Ideally, the polygrapher should have received any information developed by background investigators before polygraphing you. And one of the relevant questions typically asked during a pre-employment polygraph examination concerns the accuracy and completeness of the information provided in one's application.

If you have a point of contact you could get in touch with to rectify the discrepancy in your application, I think it would probably be best to do so before the polygraph.