Ezra and Ian,
Right now your Item Numbers are defaulting from No. Series setup, you can change this to not default so you can enter your own item numbers.
Here's how to change this:
1. Using the search type in No. Series
2. Click on the No. Series with the gears to the left.
3. Scroll down in the No. Series list until you see the ITEM code.
4. There is a checkbox "Default Nos." if this is marked the Item Numbers will default, if you unmark this then the Item Number will not default.
5. The next checkbox "Manual Nos." make sure that is marked so you can enter manually the Item Numbers.
Hope this helps!
Regards,
Jennifer Reinhardt
Please see our Dynamics 365 Financials Support Team Blog for helpful information:
blogs.msdn.microsoft.com/dyn365finsupport