Is that really that unusual though? Can you think of a situation where not asking the FBI to not follow you around the house would be reasonable?
And why would the FBI assume he was typing the invoice? If you ask me for certain documents I actually possess, depending on the document I might be gone 10 to 15 minutes as well, or even outright say that I need to find it first, I'll bring it to <X>.
I mean, if the FBI drops by for a chat, encouraging them to stick to the living room is probably not unusual. But if you're being asked for a document present in your house that's going to take 10+ minutes to find, inviting the agents along or bringing the relevant folders/computer/whatever to where they are sounds pretty reasonable.
Not necessary, which is obvious from the agents agreeing to this request. But maybe a good way to forestall concerns like "what if they think I'm forging the document right now?"
And why would the FBI assume he was typing the invoice? If you ask me for certain documents I actually possess, depending on the document I might be gone 10 to 15 minutes as well, or even outright say that I need to find it first, I'll bring it to <X>.