Gallery Slider Time

I have a standard gallery in a post and I just found out that if I set the post format to Gallery a slider appears above it, in the featured image space.

This is pretty nice, but I want to change the speed of the slider, and maybe the number of images it shows (it seems to be 6 now and I want to slide through them all).

How can I do that? Is there a setting or do I have to modify a .js file?