Increase or decrease the value of the variable by a step value.
Step value Specifies the value of step for increasing the value of the variable. The step value must be a number.
Increase/decrease first character for string The option is useful to increase/decrease the alphabet, and it's only available for the string value.
For more information about the expression, please refer to Variable and Expression.
If the current value of variable is not a number(example: string "abc"), it will be as number 0.