Aside from reading that arrow correctly, the reason you put the cone/cup spacer is to allow bolts to sit straight into the brake mount post even with slight angle introduced by your 60-to-80 mm adapter which changes the angle of the brake caliper in relation to your fork/mount. If you, for example, use these spacers between the post and adapter or caliper, then your bolt would sit directly on angular contact surface of the caliper - that can potentially snap/crack the post by applying perpendicular force to the post.
So, it's very important to follow the direction in this particular instance.