rubber title

I have a question:

What are those numbers near the ittf symbol on tension rubbers

ect. like killerspin fortissimo or tenergy they have like a box (on rubber sheet saying Ittf approved 15-003 ex 

Hi Sam,

As far as I can tell the first number is the manufacturers number.  For example all the Butterfly rubbers will start with 14 - . The second number is dedicated to a particular number.

If anyone knows more please let us know.