i think in my opinion every baby is different DS was 8.11lbs(3.940) 50cm long and DD was 8.6lbs(3.800) 50cm long and they both wore 0000 for a month and the only reason we went to 000 is we got bored with their clothes yet my bestfriends boys werent much bigger never fit into 0000 and if they did it was only for a week
and all babies grow at different rates
every brand is different also my kids always grew out of bonds much earlier then any other brand