Internal memory organization of Samsung NAND flash K9WAG08U1D
For the uninitiated : Data sheet hunting
First place to look is usually near the end where they will have a complete breakdown of order codes by part, unfortunately not the case with samsung so we will trudge on
Clue 1:

Clue 2

Clue 3

Clue 4

Combining these clues tells us

K9F4G08U0D - 4Gb variant, pinout variant 0
K9K8G08U0D - 8Gb variant, pinout variant 0
K9K8G08U1D - 8Gb variant, pinout variant 1
K9WAG08U1D - 16Gb variant, pinout variant 1

So, this flash comes in 4Gb, 8Gb, and 16Gb versions. There are two package variants of the 8Gb model in order to be downward pin compatible with 4Gb version (variant 0) or upward pin compatible with 16Gb version (variant 1)