CAD tip # 11898:

This table is then dynamically updated when you delete or add new blocks. The blocks are specified in the wizard, so their specification is stored in a DXE definition file. You can invoke the table update either manually (DATALINKUPDATE), or it is performed by default before the commands PLOT/PUBLISH, or you can add it by setting the DXEVAL variable also to the Save event.

Using data extraction to create a counter is illustrated in the video:

The resulting value from this table can be then further linked to a specific property of other drawing objects (e.g. size) - see XLSparam - tip 11896 or referred (dynamically, see Insert>Expression>Cell) from a different table using a field/expression.