One of our customer orders 100 black t-shirts size M on January 22, 2015. Currently, we have 120 in our inventory so we can ship them without any problems. The customer wants to have them delivered on November 18. We enter a sales order with the shipping date and release the order.
The next day, another customer calls for 40 black t-shirts size M. Our inventory is still 120. This customer wants to have them delivered on May 31. We enter the sales order without a warning. Lastly, we will create a new sales order for 90 of the same t-shirts with a delivery date on July 25. Now, we get the following error message:
And if we now go back to the second sales order and re-enter the quantity, we get a similar message.
The reason this happens...