You can assign an initial value to the variable when you define it, such as:

integer variable Index is 1

integer variable Box_XCenter is (BoxWidth/2)

The type that you specify for a variable determines the type of value required for the initialization (if any). Wherever an integer or floating point value is expected, you can use a negative value, such as -2 or -43.21. Wherever a boolean value is expected, you can specify a negative boolean, such as:

boolean variable Using_Dummy_Data is (not LoggedOn)