I'm a bit confused???

Let me first say, my "baby" will be 23 years of age in November. So I am not overly familiar with baby clothes, etc. Anyhow an email pen pal is expecting a boy in a couple of weeks times. So I went to the store to pick up a couple of things. She is having a boy and as they live in Australia, I figured I would get something for when he is around 6 months old, and by that time it will be the height of summer over there. You see I thought this through.

Anyhow here is what I got, pretty cute eh? They are all for ages 6 to 9 months old.



I then saw this little outfit and thought this was also cute. However, it says its for an 18 month old? It looked a little small to me.



So when I got it home I compared it to the other ones and honestly there is hardly any difference between the sizes.



They are all made by the same company, so what's up? I guess you really can't go with the sizes they say, can you?