Knitting measurements - can someone please explain?!

[MinnieMummy]

My friend's Gran is going to knit DD a cardigan. She has asked me to pick from the measurements below:

6 - 12 months

chest 20"
actual 22.5"
length 12.5"
sleeve 8"

1 - 2 years

chest 22"
actual 24.5"
length 15"
sleeve 9.5"

My question is, what is the difference between 'chest' and 'actual'??

If someone could shed light on this I'd be grateful, I'd like to get the measurements right!

chest is the size of the child, actual is what the measurement of the garment will be when made. so measure your dd if she is a 20" or under chest size do 6-12 if she is above do the 1-2. the actual garment size needs to be bigger than your childs chest size so it can go over clothes IYSWIM?

Ah, seems obvious now! Thank you!