Why is the Universal RP Depth of Field Focal Length value clamped between 0 and 300 in Bokeh mode?

Hello, I'm currently working on a Unity project, and I need to set my Universal RP Depth of Field Focal Length value in Bokeh mode above 300, but it seems I cannot. I don't understand why this value is clamped considering real cameras focal length can go above 300. Thank you!