Thanks for comments, the problem appears "...year+" ago and is still actual. In current manual the autonaming procedure was described
By default, each new group, block, or symbol is assigned a
name automatically. These names are numbered, and the
number increases by one whenever you add a new group,
block, or symbol to the drawing, ensuring that each has a
unique name. By default, the generated names are "Group 1",
"Group 2", "Block 1", "Block 2", "Symbol 1," "Symbol 2,"
and so forth.
You can change the default naming settings in the
Auto-Naming page of the Program Setup (Options /
Auto-Naming). See "Auto-Naming" on page 47.
The â€œ@â€ symbol is a placeholder where the actual number
will be inserted."
-The end of citation-