Click the Arrowhead button on the Dimension window for these options:
Position: The dimension line can be positioned inside or outside the extension line.
Offset: Enter the amount of offset.
Arrowhead: Use the Type and Size boxes to specify the arrowhead options you want to use. You can define two different arrowheads if you check Enable different arrows.
Same As (hand icon): Click to copy the properties of an existing dimension.