The guarantee section is headed "Two Months To Decide" and sits under the line "Try It Risk-Free."
It restates the 3-6 weeks window for noticing a difference and attaches the 60-day, purchase-date guarantee, so the evaluation window and the refund window overlap by design.
If a difference is going to show up in 3-6 weeks, a 60-day window leaves you time to judge and still ask for a refund. Start tracking from your first serving.