interview is for eligibilty then. order gcms asap if not already done in last 10 days. these fresh notes can give you an idea as to why have you been called. where is the interview and are you living in pakistan.
check this post. @Shereef notes. his ss just before pr.
http://www.canadavisa.com/canada-immigration-discussion-board/threads/aor-in-september-2016-good-luck-all.449402/page-67#post-6220267
have you ordered new gcms notes. this might nlt be related to ss as hou are already undergoing verification (work, funds e.t.c) and the email might be reffering to that.