Structure of Instance Identifier in TN

Hello to all,

Can anybody tell me how the Instance Identifier from the TN ist structured.

For Example:

I have the Instance Identifier:

0336a675184149f300054078

and

0336a675184149f30005407c

or

0336a675197a99f30005407c

As far as I can see the First Part is always the same: 0336a6751 and the rest is different. (Is there the Date and Time Coded ?)

Is there any need that this Format is used or can any Format be used ?(like: %Date%%Time%%RandomNumber%)

Best Regards and Thx in advance

Michael