The “Total estimated cost change” measure is created by eazyBI to track the changes of the numeric custom field and should be created in eazyBI only when you have the “Import change history” option enabled for the numeric custom field. This measure used with the Time dimension would show how the value has changed over time.
The “Total estimated cost created” measure should be always holding the latest value of the numeric custom field. Please, contact our support if this is not how these measures behave in your case.