A sequence of ranges to specify the repetition can also be used in a special group called repeating unit with repetition ranges.
See the figure below for an example.
In this example, the repetition range is 3,5-7. The repetition count for the included structure can be 3,5,6, or 7.
Syntax of the Repetition Ranges
The repetition range can contain ranges and numbers, these elements must be separated by commas. For example, 3, 5-7.
Draw a Repeating Unit with Repetition Ranges
Draw the structure.
Click the Create Group tool on the toolbar and select the structure to be included in the range.
In the Create Group dialog window, choose the type Repeating unit with repetition ranges from the Type list.
Set the repetition ranges.