Positve margins means that the dysplasia extended to the end of the sample. Meaning that there most likely is more dysplaisa in the cells. While it could be deeper into the cervix, it most likely is that the Doctor may have missed some dysplaisa on the surface.
I'm suprised that the Doctor is doing another leep so soon. You haven't had time to fully recover from the first. Did he do another colo/bio to determine if there is any dysplasia left? Sometimes they can burn the rest out when he cauterizes the ends. Well either way, best of luck to you. Hopefully he'll get it all this time!