With this contract, I currently am supposed to have 1.42428115TH/s. Should my "Principal" also be 1.42428115BTC, or something similar?
http://puu.sh/jEQSx/047c6fe155.png
No, your principal will not grow at the same rate as your mining speed. That seems to be correct the way that it is.
Hmmm, but doesn't the .42ths come from "reinvesting", thus adding to the principal?
If not, then what is the purpose of autorebuy? To hope thT difficulty drops and you have ahigher hashpower and break even quicker?
yes it does, think of it like this on a per block basis...
You have 1 TH/s of mining power and are owed 1 btc. A block is solved! You get .0001 btc as your payout for having 1 TH/s of mining power and .000025 of that is profit and .000075 goes towards your principal.
Now without reinvest on, you have .0001 btc in your account and are still owed (1 - 0.000075) .999925 btc back from the PACMiC contract. You have a total of 1.000025 btc since you made a little profit.
Now with reinvest on, instead of that bitcoin going into your pocket, it just buys more hashpower. You have your hashpower increasing by .0001 btc (because that is what hit your account from the payout from the block), but your only owed 1.000025 btc since that is all your profit was.
Alright, Thanks. I have no idea why I have autorebuy turned on then.
Because you earn more over the life of the contract. Your interest will also be compounding.