Source Table Configuration - Value for 'Join Rank'

Hi Guys,

Good day!

I would like to ask on how does the Join Rank works in the data flow.
The current value of the source table's join rank is '0'. I'm not sure on what value should I input.
The DOP of my data flow is currently set as '2'.

Also, I would like to ask for the following to further understand this function.
     What are the impact of changing the Join Rank value?
     If I update the join rank value, are there any other configuration that I should change?

Thanks,
Neil