AWS Dynamodb limits for items size and list item count sounds contradictory

Dynamodb documentation [1] clearly states that:

• "Item size" cannot exceed 400KB.


• "Number of elements in a list": An attribute of type List can contain more than two billion elements.

I must be misunderstanding something here, if you have 2 billion items in a list attribute, then the item containing this attribute is surely larger than 400KB, right?

What am I missing?

1- http://ift.tt/1senaCU