Sep 16: Recording of "reduced interest rate on your existing account" scam

Woman's voice: "Congratulations. You have been prequalified for a reduced interest rate on your existing account. Press one now to speak with a representative so your new rate will take effect. If you have received a reduced rate within the last forty-eight hours, please disregard this message. Again, press one now to speak with a live agent and reduce your rate. Or press two to discontinue further notices. Thank you and have a great day."

What is this "last forty-eight hours" nonsense?