This site's own buyer checklist closes with this specific sixth step — worth understanding it on its own.
This site describes it directly: note your guarantee window the day your order arrives — worth reading this as the practical, action-oriented close to the full six-step sequence.
This site states this same calendar-your-deadline instruction both in its own guarantee section and again as the sixth buyer-checklist step — worth reading that repetition as this site emphasizing it as a genuinely important action, not incidental advice.