Their premine is how many tokens they buy themselves with their own BTC.
Since the BTC goes to themselves there is no cost, adjusting for whatever % they want ...
An easy math task for you - how much BTC is required to adjust it to 99%?
I see you don't deny the premine is how many tokens IOTA will buy for itself.
Adjusting for a certain % is irrelevant ...
There is no premine at all. Individual team members must use their own personal funds to purchase their own personal iotas. All funds raised here goes to development of IOTA ecosystem which includes hardware.
Is there a theoretical possibility that we could lend bitcoin from someone to 'cheat' the system? Yes, this is true for all crowdsales whether it is Ethereum or IOTA.
We promise that this is not something that we will do and that's all that we can do, it's entirely up to you if you want to buy iotas or not.