Version 3 E-forms use a different method for calculating client side values. Version 4 was upgraded to a more secure method. New E-forms will be set with V3 Compatibility turned OFF. It is recommended that you leave this setting turned off. 


If you are upgrading a V3 form to V4, it would be wise to try to turn off V3 compatibility. You may need to make changes to your client-side scripting but the gain in security is worth it.