linux disk full but is not really

# df 
Filesystem              1K-blocks      Used Available Use% Mounted on
/dev/mapper/sda3_crypt  478007224 417585580  36117160  93% /

# df -h
Filesystem              Size  Used Avail Use% Mounted on
/dev/mapper/sda3_crypt  456G  399G   35G  93% /

# du -hs --one-file-system /
399G	/