- Max of 4294967296

The Sequence is a standard TCP packet header.  This header is initially set to a a number between 1 and 4294967296 and is then incremented for every byte sent.  The receiving server then sends back the same number as an "ACK" or "Acknowledgement" and is used as error detection.  

This can and is used for fingerprinting as some browsers and operating systems do not generate this in a truly random fashion.  By leaving this as default we do use PRNG however this may be used to fingerprint you if what you are using is not!  Changing this is recommended.