Pattern masking values that are marked unique and greater than their field length are now shortened differently to ensure data integrity. Previously, the custom pattern value was shortened before the record ID to meet the maximum field length. Now the appended record ID is shortened before the pattern value. If the field value is still too long after the record ID is shortened, you’re prompted to edit your custom pattern value to ensure uniqueness.
Where: This change applies to Lightning Experience in Enterprise and Unlimited editions.