The '. inc 1 st at the end of next and foll 9 alt rows..." is going to take 20 rows (10 knit rows). If you call the next row, row 1 then you would increase at the end or rows 1,3,5,7,9,11,13,15,17, and 19 and at the beginning of rows 5, 11 and 19. After that, there are the increases on the 2 following 4th rows.
Very cute pattern. Thanks for the link.