To make changes in the device configuration click the "Changes" button in the upper right corner of the web interface. 

The "Applying global changes" window contains a table of parameters whose values have been changed by the user. If you want to undo one change, click the "Roll back" button near the entry. If you need to undo all changes, use the "Roll back" button at the bottom of the window. Changes will be saved to the device configuration by clicking the "Apply" button.