As reported at the Friday The 13th blog & Variety:
…Friday for “13th,” which was playing at 3,105, registered an 86% drop. Though steep, such declines are typical for slasher fare. In its first eight days, “13th” has pulled in $50 million.
Much like a lot of the latter installments of the franchise, Friday The 13th started off strong and then nose dived in week two. It seems to be a common practice in slasher films, but more so Friday The 13th sequels as most of the post-Part IV sequels dropped off sharply after week 1.