This value is bounded by v-sync which is enabled by default in Cocos2dx. Nowadays the majority of displays have 60Hz frequency, that’s why you’ve got 0.017 sec (1.0 / 60.0).
Actually this is not the problem at all. There is no sane reason to have more than 60 FPS in video-games, especially on handheld devices. It’s more important to have stable framerate without noticable spikes than to have over9000 maximum FPS.