Some hyung have another layer of application that is taught using
an application of the hyung in ways other than the standard or most obvious bunkai. Different practitioners will learn or discover alternative applications, but the bunkai, like the hyung, varies based on the style and the teacher.
A single hyung may be broken into anywhere from a few to a few dozen applications, and the same sequence of hyung moves may sometimes be interpreted in different ways resulting in several bunkai. Some martial arts require students to perform bunkai for promotion.
Bunkai can be obvious or elusive depending on the technique in question, the moves preceding and following it, and the individual practitioner. There are usually many stages of depth of comprehension of bunkai only reached through the passage of time.