unsets either the nth bookmark (0 through 9), the next (+1) or previous (-1) set bookmarks, the bookmarks designating the start (<) or end (>) of the most recently pasted text block, the automatic (-) bookmark, or all (*) bookmarks, making it as if they had never been set; see SetBookmark. If no option is specified, n is assumed to be zero.
While you can unset the automatic bookmark ‘-’, it will be
reset automatically to the current position whenever a
command is issued.