In the first one, you relate what you've learned to the present situation: you've learned a lot = you know a lot You can say that when you're still working in that office (and you can still learn more) or when you're leaving it. pleasehelp I learned a lot at the office. Using this one, you are speaking of an action in the past, irrelevant to the present situation.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
pleasehelpI learned a lot at the office.Using this one, you are speaking of an action in the past, irrelev
Grammar Geek
As you know, you don't use present perfect with a specific time reference.
That's why I asked. I'm just wondering if he deliberately wanted to override that rule to emphasize the importance of his decision not to step down. So probably just a slip of the tongue.