Why does changing timeo attribute on NFS mount fails ?

Issue

• Not able to change the timeo attribute on NFS mounts. For some reason the value is not taken:

  [root@node1 /]# mount -o tcp,soft,timeo=10 30.5.175.15:/vol/ngtestvol /mnt
  [root@node1 /]# grep test /proc/mounts 
  30.5.175.15:/vol/ngtestvol /mnt nfs rw,vers=3,rsize=65536,wsize=65536,soft,proto=tcp,timeo=600,retrans=2,sec=sys,addr=30.5.175.15 0 0