The guarantee post's web address and title refer to a 180-day results gap. Most of the page says 90 to 180 days.
180 days is the upper end of the suggested range, while 90 to 180 days is the full range. The post's title uses the upper end, which makes the gap look as large as it can be, and the rest of the page uses the whole range.
It is probably a shorthand choice, but it is not the same statement.
Use the full range as the fair description: the brand suggests 90 to 180 days, and the guarantee is 60. For planning, the 90-day end is the practical minimum, the 180-day end the long run. A consistent description would help a reader, and you are right to notice when it is not.