Dear Rod

I am testing out the ozpost and I tried to checkout an item 36 x 13 x 17 cm , the 3kg regular satchel option still appears however in fact this item can't fit entirely inside 3kg regular satchel. I need to adjust by changing one side 13cm to 14cm.

I am wondering how does ozpost calculate whether item fit or not fit in satchel? what volume does ozpost use for 500g and 3kg satchel?

Thanks.