Susan:

There are two fields

Quantity Originally Ordered - self explanatory and cannot be edited after the order is posted
Quantity Remaining on Order - which is reduced to zero as you ship or can be increased manually (as per your example)

Quotes from the Quantity Remaining on Order (essentially what you asked for) doesn't work as a field to use for creating a new quote as this field counts down to zero as the quantity is shipped.

What you want then is the ability to edit the Quantity Originally Ordered, which then needs to update the Quantity Remaining on Order, so that any changes to order quantity is reflected in future quotes.

Seems simple enough but I'm not a programmer. This isn't a "Bug" or even a flawed logic as the logic fits the available fields in OE.