Looks like the roof of a building, perhaps his residence. My guess is that is the bike of his young daughter Kim Ju Ae, and he wants to learn how to fix a tire to look good in her eyes, or simply away from her to not look ignorant about such things in her eyes. Notice the attentiveness of all the officers present, rather than appearing nonchalant, because they already possess the knowledge, which they would, not having grown up with servants to do such things. Working for an absolute-supreme-leader-dictator requires good acting skills, and in particular, to never appear smarter than your boss.