It appears the "Invested" number doesn't change for divested amounts, but always changes when new amounts are invested. I divested with no change to the "Invested" number, then reinvested the same amount and the "Invested" number changed by the exact amount I invested. I wonder if divestments of a certain size don't subtract from the total "Invested" for some reason.
Are you sure about that?
The way I think it works is as follows:
When you invest, 'investment' goes up.
When you divest, 'investment' goes down.
When players win and lose, 'investment' doesn't change (although 'BANKROLL' does).
So your personal 'investment' figure represents how much you invested, not how much you have left of your investment right now.
Then, at the end of each week they divest your investment, charge commission on any profits, and reinvest it. The divest makes 'investment' go down. The reinvest makes it go back up, but not as much as it went down (if commission was charged).
Some examples (each paragraph refers to a separate user account):
* You invest 10 BTC. Someone wins, reducing your investment by 10%. Your investment figure still shows 10 BTC. You fully divest and withdraw. Your investment figure shows 1 BTC even though your account is now empty. (You invested 10 BTC and only divested 9 BTC, so in a sense your net amount invested is 1 BTC, which is what it shows). You leave the site and never return. That lost 1 BTC forever contributes to the 'invested' figure at the top of the screen, even though it is no longer in the bankroll.
* You invest 10 BTC. Someone loses, increasing your investment by 10%. Your investment figure still shows 10 BTC. You fully divest and withdraw. Your investment figure 'should' go to -1 BTC, since you've divested more than you invested. That's the site's signal to charge you commission. They charge you 10% of the 1 BTC profit you made, and set your 'invested' figure to 0 BTC.
* You invest 10 BTC, earn 1 BTC the first week, lose 2 BTC the 2nd week, earn 3 BTC the 3rd week. After the first week the Sunday commission run auto-divests your 11 BTC, taking your net invested amount to -1 BTC, so they charge 10% of that, and set 'invested' to 0, then reinvest the 10.9 BTC you have left. At the end of the 2nd week you have 10.9 - 2 = 8.9 BTC, and your 'invested' stat is 10.9, so when they auto-divest you then, your 'invested' figure drops to 10.9-8.9 = 2 BTC. You don't pay commission since that's not negative, then your 8.9 BTC is reinvested, taking your 'invested' stat back to 10.9 BTC. At the end of the 3rd week you have 8.9+3=11.9 invested, your 'invested' stat is 10.9, so the auto-divest takes it to 10.9-11.9=-1, you pay 10% of 1 BTC in commission, then your remaining 11.8 is reinvested, taking your 'invested' stat to 10.8 BTC. Notice that you've earned 1+3 = 4 BTC and lost 2, for a net profit of 2 BTC, and paid a total of 0.2 BTC in commission, as you would expect.
Maybe DiceBitcoin can confirm that's how it works, because I could be wrong, but it makes sense to me. The 'invested' figure is a neat way of tracking how much commission you are due to pay. It prevents you from paying twice on the same amount (in the 3rd example above you only pay 0.2 BTC in the 3rd week despite earning 3 BTC that week).