A condition preventing registration if the field does not contain at least a certain number of characters ?

Is this field a varchar (number + formating) or a integer (number only)?

If it is an integer field then you can specify the minimum and maximum value via Studio.

hello André, how can i specify the minimum value via Studio in my case ? 

You can find it here. You need to make sure that the target field is an integer one, then both attributes Max Value and Min Value will be available.

You can find it here. You need to make sure that the target field is an integer one, then both attributes Max Value and Min Value will be available.