The commonly quoted margin of error value for the 400 Series' depth range is < 1%. In real world terms though, depth accuracy can vary depending on distance and the selected resolution. The greater the distance, the greater the margin of distance measuring error that can be introduced. Using a medium to high depth resolution (848x400 and upwards) can help to reduce this.
The key phrase, then, as described by the document you linked to, is "less than one percent of the distance from the object".
Thank you for your response, but I don't know why the datasheet https://software.intel.com/sites/default/files/Intel_RealSense_Depth_Cam_D400_Series_Datasheet.pdf does not say 1%, when the test set up to measure depth accuracy as described in it, is measuring the distance from the object.
Also - I am looking for information about the distribution of depth measurement error. Is it 0 mean?