ls -l Vs df

Hi,


DATA:
   I have an embedded linux system. It contains an 8 MB NAND Flash
jffs2 filesystem. There are 4 partitions:

 P1: bootloader
 P2: kernel - v2.4.18
 P3: Flash fs (1MB)
 P4: Linux root fs

 Only the flash fs is writeable.
 The system was cross-compiled with mipsel linux gcc.
 The problem below is with regard to the flash fs only.

PROBLEM:
  The memory usage displayed with ls -l does not tally with what I get
with the df command. Why? For example:
#ls -l
   -rwxr--r--    1 root     root        17315 Jan  1  2004 x1
   -rwx------    1 root     root       133790 Jan  1 00:22 opfile

# df
Filesystem           1k-blocks      Used Available Use% Mounted on
/dev/mtdblock2            1024      1020         4 100% /mnt/disk


CONSTRAINTS:
The system uses busybox instead of the entire set of linux tools.
Therefore, commands like du, top etc. are not available.

 Please let me know what's wrong and what other info u might need.

Thanks and Regards,
Karthik