Something doesn't quote add up:
Site Bankroll: 389,800,231.98 bits
Wagered against bankroll: 14,589,464,076.97 bits
Investor Profit: 87,654,258.75 bits
Your stake: < 0.01 %
Your amount: 100.86 bits
Today:
Site Bankroll: 389,934,103.16 bits
Wagered against bankroll: 14,772,889,421.86 bits
Investor Profit: 99,064,021.05 bits
Your stake: < 0.01 %
Your amount: 103.90 bits
So collectively the gamblers lost 99,064,021.05-87,654,258.75=11,409,762.30 bits, which is a 13.0% increase. The site bankroll barely budged, making only a 0.03% increase, meaning the investors collectively divested 11,275,891.12 bits. Ergo, gamblers lost a ton of money, the other investors divested a lot of money, and I only get a 3% increase? Note: I did not divest any of the 100.86 bits that were already in there. So either moneypot is faulty or the formulas are more complicated than that (unless I'm wrong)...
It's probably the last one
Let's illustrative purposes lets the bankroll was 100 BTC, and you own 1% of it (1 BTC), and the investor profit has been 0.1 BTC. Now let's say a gambler comes, and loses 1 BTC.
That means the investor profit has gone up from 0.1 BTC -> 1 BTC (1000%)! How much would you expect to make?
Well you don't make 1000% of your money, that's for sure, because if so you would've made 10 BTC (that's more than the gambler lost!). But rather, your profit would be { your stake} * { increase in bankroll } or 0.01 BTC (You own 1% of the bankroll, so take 1% of the loses and gains).
So back to the moneypot example, the change in investor profit is actually meaningless. What you care about is a gambler lost ~11.4 BTC on a ~390 BTC bankroll which means the bankroll should have increased by ~2.92%, and thus your stake should be worth the same amount more. Which matches your observation.
BTW a very probable reason the amount divested almost exactly matches the amount lost, is because the person who divested the money is the same person who lost it
(Disclaimer: I'm not an investor and haven't been following MP, I'm just going purely based on the info in your post)