Field help (VCCE) 

This field is used to enter the analytical dimension code.

The setup length of the code is used to define the maximum length of a dimension and dimension type code by dimension type.
It is possible to use the * and ? wildcards to include several dimensions into a template.
The dimension must not be included in another group in the same dimension pyramid.
Similarly, the same group name can only be used once, in a pyramid and a dimension type.