It is typical for the UL (in urn form) of each Leaf entry to end with .xx7fxx7f

Any Byte value 0x7f in a UL is a “wildcard” that is substituted in implementations by a range of permissible values specified in a defining document.

For example, SMPTE ST 381 specifies that Byte 14 of the Frame-wrapped MPEG Data Element is set to the number of Data Elements in the Data Item of a Content Package, and Byte 16 is an index to make each instance of this element type unique.