It just means your baby is bigger than the average baby at the same age, I think it's usually not a cause for concern unless it's at a really high percentile (90% percentile or more - means your baby is bigger than 90% other babies the same age) which might make delivery more difficult and more likely to require c-section.
The size and length is just an estimation. It could be slightly ahead or behind the gestational age (+/- few days). As Long as the gynae say is ok, there’s nothing much to be concern about. If you are concern, u can ask the gynae during ur next scan on the spot whether the size is ok.
Hi, baby grows differently depending on mummy's diet. As long the weight is okay, it should be fine:)