It sounds like your baby is smaller in size but weighing fatter. Tbh, it’s not a huge issue because weight is just a rough estimation, there are many cases where baby weighing 3.5kg and less than a week being delivered at only 2.8kg. There is a 20% in weight differences. So actually if you’re week 24 and baby’s weight is week 25, it’s nothing alarming. Follow your gynae’s instructions and advice