I have not provided a specific part on the Part Sourcing tab of CDIF however when I download the master data file from the Resilinc system, I see this part listed on this tab.

Created by Atif Ikramuddin, Modified on Wed, 27 Aug at 1:56 PM by Atif Ikramuddin

This particular part has been provided by you on the Part Site Mapping tab hence it has started showing up on the Part Sourcing tab of CDIF even though you have not entered it on this tab.
Note: this is applicable for Partners too. If you have not provided a specific partner on Partners tab however it has been entered on any other CDIF tab then it will start showing up on Partners tab when you download the Master Data file.