21 1. Lua programming Monitoring variable Step 1: enter “v1” in the monitoring variable window. Step 2: set 50 for $100 on the HMI. Step 3: click on the arrow button to carry on the execution in the Lua program editing window. Step 4: Lua program runs and then stops again at line 13, where the breakpoint is placed. Because of the instructions of line 9 and 11, “v1” reads the value of $100 and plus 1, then “v1” in the variable monitoring window is 51.