Max Length and Min Length

Hi,
use Regular Expression in the Validate as field in the Edit as settings dialog on the Visual Editor tab.

Here is a sample expression: [0-9]{8}

Dear I did expression: [0-9]{8} , but once i enter 8 digits it showing error , what I need I want to inforce the user to enter 8 digits only , not more and not less, so when he enter less then 8 digits or more then 8 digits, then he will get error, but with 8 digits should be ok.
regards.

it was my mistake, it's work , thank you so much.