Where to choose size of the shock?

In ‘Fiscal Volatility Shocks and Economic Activity’ by Fernandez-Villaverde, Guerron-Quintana, Kuester and Rubio-Ramirez (2015. AER), they study the economic impact of a 2 standard deviation volatility shock to capital tax rates. I want to see what happens when I have only 1 standard deviation shock to capital tax rate. I looked at their replication files but could not figure out what in their code determines the size of the shock so that I can change it. Will appreciate any inputs. Here are their replication files main_code_FGKR_20121236.zip (17.9 KB) .