Amigurumi: What does sc in next sc mean?

It means that you should only make one sc in the next sc. In other words 2 sc, 1 sc 2sc 1sc in the sc of the lower row. That is how you would work the pattern but look at it before you go to the next row because as for the many years I have been crocheting I still make a mistake and put one sc in the two sc or Viceversa.