What percentage of Marcus's ancestry is Asian?

In David Henry Hwang's play, Yellow Face, the playwright tells a fictionalized story based on his own real life experience of backlash for casting a white Brit as an Asian character in the play Miss Saigon. Similarly, in Yellow Face, the fictionalized Hwang casts a fully white man named Marcus G. Dahlman as an Asian character in a play. In the play, Hwang hires Dahlman believing that he has Asian ancestry, and tries to convince others that he does have Asian blood as a "Jew from Siberia." Hwang eventually realizes that Marcus has no Asian blood at all, but by the time he makes this revelation, it is too late to change the casting or cancel the play. Marcus is so invested in playing an Asian character that he continues to maintain the claim that he is Asian for the rest of his life, even becoming an Asian rights activist later in his life. While Marcus does not actually have any Asian ancestry, he eventually adopts an Asian identity, much to the annoyance of Hwang.