I love all these attempts to make sense of calories-in/calories-out.
You simply cannot make anything useful from these figures. Unless you write them down on a piece of paper, and use said paper as a fire-lighter.
Firstly, your estimate of calories-in is probably completely wrong. Secondly, you're assuming your body can assimilate all of those calories and use them. Thirdly, you're assuming your body will have stored any excess calories (whatever that statement means) as fat.
Truth is, you simply don't know. All you know is that you returned from holiday heavier than you left. Maybe you added some muscle because you were hefting luggage about? Maybe your blood volume went up because it was hot? Maybe your high-fat diet has left you incredibly constipated (a few days of backlog would probably easily account for a kilo of your gain (Yewww!)) Again - you just don't know.
Assuming it's body fat you're concerned about, it accumulates quite slowly - certainly slower than you could detect in six days.
When it comes to over-eating, you can only really use that information in retrospect. If you put on body mass of any kind (fat, muscle, connective tissue, a baby) you have to have taken in more calories than you used for staying alive, that must be true. But you cannot use calorie/exercise burns to predict whether you'll lose or gain weight.
If you want to lose fat, you have to start by encouraging the right hormonal conditions for your body to do that. It has all the machinery ready and waiting - you just have to give it the right conditions. Once you do that, then you can work on encouraging your body to actually burn the stuff - by eating less (NO! Don't count calories, just eat when you're hungry), and by keeping active.
