A Root Class is a class that is defined as a Root in the Class rules
When Number Root is set it indicates that the tagname of the symbol parent/grandparent etc symbol with the Root Class is to be used as the Top level in symbols whose class RealTag uses Root based tagging methods.
For example you may have several process cells, containing many Units. All the tagging can then be made based on the units tagnames
When Number Exclude is set it indicates that the tagname is excluded from the RealTag of descendent symbols whose class RealTag has 'with exclusions'
Typically, and in the standard ControlDraw models, S88 Units are number roots. This generally works well.
See Also Hierarchical Tags