@Syana344, there has been plenty of discussion on this over the years, especially since the Authors list was added. But, basically, jackie_w is right.
Kobo is assuming that authors are in "LN FN" format. And for multiple authors, it is "FN1 LN1, FN2 LN2". In the book list, it will use an ampersand as a separator as well, but the authors list doesn't.
The other big thing is that the firmware only reads the first dc:creator tag in the OPF. And only takes the value. It doesn't look at the file-as that is calibre uses for the author sort.
Because of this, I use the following metadata plugboard to set the author:
Code:
program: raw_list('authors', ', ')