It was my believe as well that when you deleted all the related roles, the profiles and entries in USR12 would also be deleted. For this specific profile the entry is not deleted. And i can't find anywhere to do this deletion.
A curious thing is that normally when i have en entry in USR12 the auth is concluded with a 00, this one ends with 01. So the normal would be xxxxxx00 and this one is called xxxxxx01.
I don't know if this has anything to do with it. The number seems to be some kind of sequence number.