Check your math.
What are you objecting to? I'll admit that in computing a diminishment of 7% per hour, I actually computed a 7% increase in the amount of currency required for each dollar of purchasing power (it should have been 7.5%). What else do you object to?
Note that if asset increases by a factor of (1+r) in each interval, its value after 'y' intervals will be (1+r)^x times its original value. The formula applies even whether 'x' is greater or less than one.