Quick Question about Certificates

[EvilAchmed]

I have been reviewing how to create and assign certificates and I think I have it pretty much figured out except for one thing.  How do you find out what certificates are assigned to a CA?  I currently only have 2 certificates created, 1 for my captive portal and one for my OPNsense WEB GUI.  I see these two certificates assigned to the CA I want to us moving forward in the Authorities section but my old CA that I would like to delete still shows a "usages' of 1.  I am trying to figure out where that is coming from before I just delete it.  Your assistance is appreciated.