Values beyond a range domain are allowed in an attribute table because there is a validation process to check if the attributes or relationships of feature do not violate any geodatabase rules, including range domains. This is by design. If an invalid value that exceeds the values defined by a range domain is typed, the value is detected by the validation process and the user must decide whether to keep or correct the record.
To maintain data integrity, users can set the validation process to notify when a geodatabase rule, such as a range domain, is violated. The notification can be set to appear during or after entering the values in attribute tables.
There are two methods to set validation to notify domain range violations.