AutoCAD Pocket Reference, 4th Edition

CENTERMARKS can ONLY be drawn with circular objects like Circles and Arcs. You set the size and type.
The Center Mark has three types, None, Mark and Line as shown below.

What does "SIZE" mean?
The size setting determines both, (A) the length of half of the intersection line and (B) the length extending beyond the circle. (See above right)
Where do you set the CENTERMARK "TYPE" and "SIZE"
Select the Dimension Style command.
Select: Modify or Override.
Select: SYMBOLS and ARROWStab
Select the Center mark type
Set the Size.

To draw a CENTER MARK
Select the Center mark command using one of the following:
<b class="bold">Ribbon = Annotation tab / Dimension <span class="unicode">?</span> panel /<span class="inlinemediaobject"><img alt="Image from book"> border="0"> height="27"> id="IMG_211"> src="https://images.books24x7.com/bookimages/id_30311/figu4-19_3.jpg"> title=""> width="27"></span></b><b class="bold">Keyboard = DCE</b>
Select arc or circle: select the arc or circle with the cursor.