This rule copies standard fields, Contract Start Date and Contract End Date, into custom fields as defined in the parameters. The parameters are the labels for the custom fields you would want copied into the standard Contract Start Date and standard Contract End Date respectively. For example, if your custom contract start date field is named Date Contract Start, like parameter 1, the value will be copied to the standard Contract Start Date field when the standard field is null. If the standard contract start date field has a value and the custom field does not, the standard field value will be copied into the custom contract start date field from parameter 1. If both the standard and custom field contain a date, the field that was last updated will be the value that gets copied to the other field. For example, if the standard field was updated Monday and the custom field on Tuesday, the value in the custom field would be copied into the respective standard field.