Switching to Dimension Symbols
On the Annotate tab, in the Parameters group, click 
Switch Symbols to show the dimension symbol, and identify the symbol type. The figure below shows dimensions that have been switched to show their symbol displays. The letter combinations define the symbol type, and the number is a unique identifier for the dimension. The letter and number combination create a unique reference designator for the dimension that is used in advanced techniques such as defining relational formulas between dimensions.
Switch Symbols to show the dimension symbol, and identify the symbol type. The figure below shows dimensions that have been switched to show their symbol displays. The letter combinations define the symbol type, and the number is a unique identifier for the dimension. The letter and number combination create a unique reference designator for the dimension that is used in advanced techniques such as defining relational formulas between dimensions.
• d—Shown (driving) dimension created during feature creation in the model. These dimensions are associative bidirectionaly between the model and the drawing.
• ad—Created (driven) dimension which is associative to the model and stored with the model but cannot be modified in the drawing. These dimensions update in the drawing only when model geometry is modified. ad dimensions result when the config.pro options create_drawing_dims_only and draw_models_read_only have values of no, which are the default values.
• add—Created draft dimension which is still associative to the geometry or draft entity which it references, but gets stored with the drawing. add dimensions result when the config.pro options create_drawing_dims_only or draw_models_read_only have values of yes. To create add dimensions for referencing draft geometry, the Detail option associative_dimensioning must be set to yes.
• dd—Draft dimension which is not associative to the draft entity which it references. To create dd dimensions, the Detail option associative_dimensioning must be set to no, which is the default value.