Meaning of * in lineage

[Reilly12]

I used the parentlineages function to look at XCF's parent and found that its parent are recombiant parents: XBB* and FE.1. Looking further at FE.1's parent I found that its parent is XBB.1.18.1, so it looks like XCF's parents are all from XBB. So What is the meaning of the asterisk in the XBB*?

Thank you in advance.