Re: 844TB of data from 12 flight hours
There's a frankly staggering amount of information available from the engines alone. I was tangentially involved in some data logging trials and like you I was out by a few orders of magnitude when it came to what the aircraft could produce.
Different users have different data requirements though, so the engine manufacturer wants to know stuff about the engines I didn't even know was a thing, which lets them develop predictive maintenance programmes that minimise down time. The flight safety department want to know all about how the aircraft is flown so they can try and anticipate where the next accident could occur to prevent it, that used a few hundred parameters more than I thought would exist too.