Hi Pramod,
The max value of max quantity is 999,999,999. Though the quantity generated tends to eat up Java heap space. You will likely find that generating the max will result in an error.
The quantity to generate should match your needs, ie 1 million in the case you described. I don't completely understand the use case but basically, set the quantity to what you need, the max to the upper limit of what can be generated. That can be helpful when variablizing the number of UUID's to generate to make sure it is not exceeded.
Regards,
Joe