need to see what Invite Codes people use to register with Membership

I am currently using Membership 2.0.7 on WordPress 3.3.1. I configured a number of Invite Codes to only allow registrants who received a special code from me. Now I would like to confirm what Invite Code each individual registrant used. I cannot find any documentation on this and would appreciate any help – I am a novice with SQL databases so I would appreciate detailed instructions. Thanks in advance, I am quite pleased with the Membership plugin and find it well worth the investment.