Hi! When you run org-clock-in and then restart emacs, clocking in again will show a prompt asking what to do w/ the unfinished entry. "i" means "ignore this question; the same as keeping all the idle time". However, a new entry is created if this is chosen without doing anything about unfinished one. Keeping all the idle time w/ "k" updates the unfinished entry before starting a new one. "i" doesn't do that, so the description seems a bit misleading.
Best, DK