This often serves as shorthand for a beauty brand or specific "Better Than You" product lines.
In streetwear and branding, "646" is frequently used to signal a "made in New York" or Manhattan-based identity. 646 bty grlzip
This likely refers to a "Girl Zip" style—specifically a full-zip hoodie or a piece of apparel featuring the trendy "grl" branding found in modern urban fashion. General Product Review (Streetwear Context) This often serves as shorthand for a beauty