so I moved my iTunes from iMac to a MacBook Pro Catalina 10.15.3 using Migration assistant. Ive always had 1 library, "William's stuff". Now it seems that I have a library called My Library and William's stuff. Sometimes I get and option to select one or the other and sometimes there is no option. See screenshots. What is My Library and why do I get an option sometimes to select it and sometime not? Ive talked to senior apple advisors with no luck - "they've never seen this before". I can't even tell where they are located..... Any help?