If you are using revisions for the calculation lines, this shows the period in which the calculation line is valid.The form behavior depends on the revision setting on the Revision management tab of the Basic data form:
If the Part revision management check box is not selected, you can change the fields.
If the Part revision management check box is selected, you cannot change the fields. The contents of the fields will be determined by the data relating to the different revisions you add, and by the release of the revisions (or the cancellation of their release).