those numbers are true but put it this way. The bond is only (and always) worth 1BTC. Say you buy 50bonds at 100BTC well you can try to sell them higher but you can always sell them back to goat at 1BTC. No matter what you pay for the bond your always getting 6.5% of their true value, not 6.5% of what you pay to acquire the bond.
In your scenario your paying 200BTC for 100 bonds which are valued at 100BTC. (each bond = 1 BTC)
That's what I was getting at. The returns if you buy at 1.02 aren't 4.4% for the first week as Raphy said since it's not like Goat is buying back the bond at 1.065. The return also doesn't change or approach 6.5% over time. It's always going to be (0.065/X) weekly, where X is what you pay for the share. If shares sell for 1.02, you'll get 6.37% return weekly on your investment.
You'll receive 6.5% of the NOMINAL VALUE of the bond, which is 1BTC. Independently of how much you pay for it.