That is what the chart shows. Sorry I can't wrap my mind around this, but your answer is still to increase the measurements by 120% How do you figure out in inches or MMs what 120% is?
Did you mean increase each piece 1.2"?
To turn a 10" block into a 12" block the chart shows to enlarge the pattern 120%. 10 x 1.20 = 12 so you would have to enlarge each template or measurement for each piece in a 10" block by 120% before seam allowances.