The “setting” refers to the setting value. The DC output accuracy is specified as ± 0.05 % of the setting value. Meanwhile, the “rtg” refers to the rated value. For example, in the case of PBZ20-20, 20 V is the rated output voltage. Therefore, the DC voltage accuracy is specified ± 0.05 % of 20 V, as well as the current.
For the details, read the user’s manual and the settings and conditions specified on the first page of the Specifications chapter.