How do you interpret the rated output current and duty cycle of a welding machine?

For example, what does "60% duty cycle" specifically mean for a 315-type welding machine

Focus on rated current, not peak current: Only consider the "rated output current"; 200A is the ideal choice.
Duty cycle ≥ 30% is sufficient: 40% is optimal, 60% is unnecessary, and be cautious about choosing below 30%.