The bidding 1C - 4H - 6D - P; P - P is not an auction you see everyday! Everyone at this table made great choices to make this a very interesting hand.
Responder’s 1NT, often called the “Dustbin 1NT”, often causes confusion in bridge learners. Many people remember the bid to mean “6-9 HCP”, “no fit in Partner’s suit” or “any old rubbish”. The truth is that these are all part of the answer: but not the whole answer! The bid should not be thought of in terms of what it shows but what it denies. It simply means “I couldn’t do anything else”. No wonder it’s so difficult to get your head around!