When Number Automatically is set in the Palette then when new objects are added (whether by dragging fom the palette or by pasting them then their tagnames are given trailing numbers according to the rules for the class. These rules are defined in the Data Design in the Auto Tag nmbering section
If number Globally is set then the numering applies across all diagrams, otherwise it applies within each diagram.
If number of digits is set to -1 then the objects are not numbered
If set to 0 then the objects are numbered with no leading zeros it greater then leading zeros are applied if required to the number.
The number of digits can be up to 6
For example if you have a diagram with XV01 and XV02 on it then the next one youu add wil be XV03