ls -ls没有显示目录的真实大小

我ls -lS在主目录中使用了命令。该命令应该按大小列出目录的内容。这是我运行此命令后得到的

total 10148
-rw-rw-r--  1 rahul rahul 8053159 May 15 15:35 Costa_ODE.pdf
-rw-rw-r--  1 rahul rahul 1755507 May 15 17:33 gnuplot.pdf
-rw-rw-r--  1 rahul rahul  218048 May 13 22:14 out.log
-rw-rw-r--  1 rahul rahul   98131 Feb 16 01:53 hs_err_pid8639.log
-rw-rw-r--  1 rahul rahul   12364 Apr 19 14:01 Untitled 1.csv
drwxr-xr-x  4 rahul rahul   12288 Jun  6  2016 cfitsio
-rw-r--r--  1 rahul rahul    8980 Feb  7  2016 examples.desktop
drwxrwxr-x  2 rahul rahul    4096 Mar 10 12:24 bin
drwxrwxr-x  8 rahul rahul    4096 May  8 14:51 boxfitv2
drwxrwxrwx  2 rahul rahul    4096 Jan 30 11:50 dao2
drwxrwxr-x  2 rahul rahul    4096 Mar 12  2016 deja-dup
drwxr-xr-x  6 rahul rahul    4096 May 16 02:12 Desktop
drwxr-xr-x  3 rahul rahul    4096 May 15 10:53 Documents
drwxr-xr-x  5 rahul rahul    4096 May  8 14:09 Downloads
.
.
.
.

它是一个很大的清单。但我希望您专注于子目录，例如“桌面”。它的大小显示为4096字节。但是，当我尝试查看Desktop的详细信息时，这就是我得到的。

简而言之，该命令ls -lS未计算桌面和其他子目录的内容大小。有什么办法吗？

编辑：

ls -lsh命令输出

total 10M
4.0K drwxrwxr-x  2 rahul rahul 4.0K Mar 10 12:24 bin
4.0K drwxrwxr-x  8 rahul rahul 4.0K May  8 14:51 boxfitv2
4.0K -rw-rw-r--  1 rahul rahul 3.2K May 13 13:28 c.c
 12K drwxr-xr-x  4 rahul rahul  12K Jun  6  2016 cfitsio
7.7M -rw-rw-r--  1 rahul rahul 7.7M May 15 15:35 Costa_ODE.pdf
4.0K drwxrwxrwx  2 rahul rahul 4.0K Jan 30 11:50 dao2
   0 -rw-rw-r--  1 rahul rahul    0 May 13 20:37 default.txt
4.0K drwxrwxr-x  2 rahul rahul 4.0K Mar 12  2016 deja-dup
4.0K drwxr-xr-x  6 rahul rahul 4.0K May 16 17:11 Desktop
4.0K drwxr-xr-x  3 rahul rahul 4.0K May 15 10:53 Documents
4.0K drwxr-xr-x  5 rahul rahul 4.0K May  8 14:09 Downloads
 12K -rw-r--r--  1 rahul rahul 8.8K Feb  7  2016 examples.desktop
.
.
.

du -sh ~/Desktop命令输出

80M /home/rahul/Desktop