What does it mean? What does it mean when "50/50 rule" is indicated?

When a program indicates a 50/50 rule it means you request a payout, you must first deposit at least 50% of the amount value you requested before your withdrawal would be honored.

Example:

A program states "50/50 rule".
You have $10 currently in your account balance.

If you want to withdraw all that $10, you must at least deposit $5.

$5 is 50% of $10, and by depositing $5 you are following the 50/50 rule.

The program administrator, or owner, will have to check if you have deposited $5 and if you have, your withdrawal request of $10 will be processed.
You can deposit $5 or $6 as long as it is greater than %50 of $10.

Some people like this rule since it makes the program "stable". When 50/50 rule is indicated, the funds would not be depleted easily since members are forced to deposit again and not "hit and run". The ratio between the amount deposited and amount withdraw will usually be broader and thus, more people would want to join the program seeing the stats are not yet nearing the end.

However, it is not a guarantee that when a program specifies a 50/50 rule, the program would last longer. Some people don't like a 50/50 rule since they don't want to deposit again and would prefer to deposit and withdraw earnings immediately.

So in summary, when a 50/50 rule is specified, when requesting your cashout, you must make an upgrade upgrade of at least 50% of your cashout request to receive your payment. Some programs would strictly specify you must upgrade BEFORE requesting a payout, and some would allow you to upgrade AFTER requesting a cashout so be sure to read the program FAQ.