[Yaffs] Wrong data after unmount/mount

Hi

I have a small question concerning the YAFFS direct implementation and
appending data on a file.

I have a file called "file01". Now I use the procedure "yaffs_write(h,
buffer, 600) to append data to the file until no more space is left (my
flash supports 512Bytes/Chunk and I reduced the total YAFFS size to
1916928 Bytes):
- Size of the file "file01": 1041408
- Available size but not useable: 875008

If I change the size of the buffer to "yaffs_write(h, buffer, 1024), I
get following result:
- Size of the file "file01": 1904128
- Available size but not useable: 12288

What happens if I add packets with size of 600Bytes? Do YAFFS use 2
chunks and in the second chunk 424 Bytes are lost (512 - (600-512) = 424) ?!