Minecraft wiki entry for History, associated text: 32,768 bytes of block data which appears to be a x*z*y = 16*16*128 block chunk.
16,384 bytes of regular data (one nibble for each byte of block data above).
16,384 bytes of skylight data (one nibble for each byte of block data above).
16,384 bytes of block light data (one nibble for each byte of block data above).
256 bytes of additional data which appears to be a z*x = 16*16 byte array (one byte for each vertical y column of 128 bytes of block data above) containing dirty column info.
1,024 bytes of additional data which appears to be a 16*16*4 byte array (four bytes for each vertical y column of 128 bytes of block data above) containing grass color info.