RE: what is the source table which displaying value in "Sales document detail inquiry zoom"
Matt is definitely right on this one, depending on the status of the document, it could either retrieve from SOP10100 or SOP30200. Although, I would like to add up additional essential point as related to how you may have an answer for any similar inquiry; GP Power tools is the answer, security profiler catches the associated tables for each screen in a neat and simple way, this will help you track down such issues when needed.
Here are the "associated tables" for the Sales Document Detail Inquiry zoom window:
Check it out on Dynamics GP Power tools Portal
Your feedback is highly appreciated,