As a residuary Legatee, I was asked to sign a renunciation to administer the estate of my aunt. I have not seen the will. What did I renouce?

Without seeing the document, it's impossible to tell.  You should have asked a lawyer before signing.  That said, from the wording you used, it sounds like there is not a will.  If a will was involved, there would have been an executor assigned, not an administrator.  An administrator needs to be appointed only when there is no will.  It sound like you signed that you would not be acting as the administrator, allowing someone else to do it.