CI Model-STRING:100 canot be extended

Hi Support,

I am trying to extend Configuration item CLASS, Model field from STRING:100 to STRING:128. When I do that from GUI (Administration Module) it seems that the change is applied however the number still shows STRING:100. I did restart the whole system and it still shows the old value (STRING:100). I also chcek the field limit on Database directly and it shows correctly the new (STRING:128) value. Can you tell me if there is any GUI limit or how to fix this?

Thank you in advance,
k.r. Petr