479 and 479
Start off with the simplest example: a dipeptide.
If there are 2 amino acids linked together, then there is only 1 peptide bond between them.
Try a tripeptide.
If there are 3 amino acids, then there are 2 peptide bonds between them.
The general logic holds for higher numbers. That is, the number of peptide bonds is 1 less than the number of amino acids.
So with 480 amino acids, there would be 479 peptide bonds.
One molecule of water is released for each peptide bond formed. There are 479 peptide bonds formed, so 479 molecules of water are released.