If you check the box O on one or several rows, a separate customer order will be created for these rows. This requires that you have used the Order... button under the Main tab.
If rows are checked in the O box a question appears asking if you want to "Create a new quote for the remaining unchecked quote rows?".
If you say Yes a new quote will be created containing the rows where the O box has not been checked. You can then choose to enter the same quote number and a new sub-number in order to create a new sub-quote. You can also leave the field empty in order to create a new quote with the next quote number loaded from the Number Series. The existing quote will be given status 9 - Order.
If you say No, no quote will be created. The existing quote will be given status 9 - Order.