Use this dialog box to change the price of a periodic price line by applying a revaluation type and to change the quantity of objects/units that are subjected for the service. The status of the periodic price line should be Accepted and you need to include a revaluation type in the Service Contract/Invoice Parameters tab in order for it to be applied here.
Once you click OK a new periodic price line will be included in the table, with the status Revaluating, you can either accept the changes (right-click and then click Accept Price Change) or rollback the changes (right-click and then click Rollback Price Change).