It almost certainly accounts for the interest that accrued from the time of your last mortgage statement until the payoff date. It's also very possible that you will get some of that extra back based on the date that the actual payoff was received and the calculated interest.
Under federal law, the servicer must generally send you a payoff statement within seven business days of your request, subject to a few exceptions. (12 C.F.R. § 1026.36.)
There's a process to getting the mortgage payoff statement. First, you'll need to contact your lender and let them know you want the information. Depending on your lender, you may have to sign in to an online account, call a helpline, or send a formal letter to start the request process.