The calligraphy works are titled "Master Yuan Hongshu". Justin is the author's name. What does master mean?

I don't know why this "Master Justin" is alone.

But signing such a signature is a bit unreasonable, or this person is a bit boastful. Whether this "master" is interpreted as "a person with deep attainments and high reputation" or "Buddhists call Buddha, which is also a respectful name for monks", it should be regarded as a kind of respectful name by others, claiming to be. ...