Those were different; they all started at the same time as him.
Having pacemakers in marathons that way is deemed acceptable. The organization of a marathon will even specifically hire runners to, say, run the first half in one hour ten minutes, after which they are free to step out of the race.
Here, each pacemaker, including the ones that accompanied him to the finish line, ran for only about 9 km (my guess, given 35 pacemakers used and using groups of 7). So, the last group only started running when Kipchoge has run for over one and a half hours.
Having pacemakers in marathons that way is deemed acceptable. The organization of a marathon will even specifically hire runners to, say, run the first half in one hour ten minutes, after which they are free to step out of the race.
Here, each pacemaker, including the ones that accompanied him to the finish line, ran for only about 9 km (my guess, given 35 pacemakers used and using groups of 7). So, the last group only started running when Kipchoge has run for over one and a half hours.