Yes the above is correct except the figure actually relates to percentages. To put my geek hat on a centile is a statistic used for comparisons, in our case babies. The number given relates to a comparison to 100 other babies (yours isn't included in the 100) of the same age, the 100 represents the average from smallest to biggest. So if your baby is on the 50th centile line for weight 50% of babies will be expected to be lighter 50% heavier. If baby is on the 2nd (like our daughter) 98% bigger, 2% smaller and so it goes on.
As with any statistics it's only a guide and I did read in the New Statesman that the maths behind the weight statistics could be quite wrong leading to obese children.
