A variable may have an initial value. The value must be a valid constant expression that fits to the data type of the variable. The initial value is displayed in red if it is not a valid expression for the selected data type.
There is no initial value for arrays and instances of function blocks.
To change the initial value of a variable, enable the modification mode in the grid and move the cursor to the selected "init value" cell. Then press ENTER to enter the new value.