Some old records
Being the lord of a large territory isn't too different from being a ruler; with the small difference that you don't get to form international alliances and the like. At most, you can collaborate with the lords of the fiefs nearby.
It's an easier job than ruling a whole kingdom, but it isn't as easy as one could imagine.
Regardless, my Duke has been doing his part excellently. I don't need much time to understand what's going on, and I do the calculations first.
I'm very fast, usually, but I keep a slow pace not to alert the sleeping man a few metres from me. It's better if he understates my capabilities, in case he's suspicious of my intentions.
In the end, I don't find anything interesting. My Duke already did most of the work, so I have just to finish reviewing the tax reports and read the correspondence from the other nobles.