Payouts are based on the percentages of investments.
If the highest investment is 1 bitcoin at the time, and address_4 sends in .5 Bitcoins. Then address_4 will always have a 50% payout rate.
So, if the highest investment sent to the main address_0 is 1 bitcoin by address_3, then address_4 sends in .5 bitcoins, address_5 sends in .5 bitcoins, and lastly, address_8 sends in 2 bitcoins. How much will each address receive in FUTURE payouts?
Easy. It's all based on the percentage of the highest investment.

Highest investment = 1 Bitcoin by address_3 = 100%(For this example, lets say the was the first ever investment)
address_4 = .5 = 50%
address_5 = .5 = 50%
address_8 = 2  = 200% (New highest investor)


Payouts:
Address_3 will recieve a weighted 100% of address_4 investment (minus the 10% that is ALWAYS kept by the main address_0) = .45 bitcoins.
address_4 will recieve a weighted 50% of address_5 investment and address_3 will recieve a weighted 100% of address_5. So hold 10% of address_5 investment for the main address_0. So the main address will keep 10% is .05 bitcoins. Address_3 will get 66.66% of address_5 = .297. Address_4 will get 33.33% of address_5 investment = .148 bitcoins.

To find the percentage, take the addresses investment percentage and divide it by the sum of all the previous percentages, then multiply it by 100. That will give you the payout percentage. Then take that number, and multiply the percentage by the next investment. But always keep 10% for the main address_0.

So we can make sure we are on the same page, tell me how much each address will get from address_8 investment of 2 bitcoins.