10 times means to decrease every other row at the armhole until you’ve decreased 10 sts. So for example you would decrease on rows 2,4,6,8,10,12,14,16,18,20. Decrease on every row 2 times means to decrease at the neck edge at the current row and also on the next row. Then the decrease at the neck edge on alternate rows (or every other row) 6 times. So for the neck decreases, you would decrease on row 1,2,4,6,8,10,12,14.