You might want to add symbolic link lrwxrwxrwx as a 3rd category besides file and directory:
[byrdeo@euler04 ~]$ ln -s a b [byrdeo@euler04 ~]$ ll b lrwxrwxrwx 1 byrdeo T0000 1 Aug 2 16:44 b -> a
- Permission bits
The numerical representation in your table (e.g. rwx = 421) is misleading because it can be confused with the overall permissions in octal form (e.g. rwxr-xr-x = 755) used by chmod.
To avoid this, it would be better to give the binary representation in the 2nd column (r = 100, w = 010, x = 001) and explain that the 3rd column is obtained by summing those bits (e.g. rwx = 111 binary = 7 octal or decimal).
- Special chmod flags
Add -X flag.