Parameter and Default Value Must be of the Same Type
From Xojo Documentation
Error message
You used a value of an incorrect data type as a default value. When you create a method in the Add Method declaration area, you can optionally set a default value for each of the parameters. Of course, the data type of the default value must match the data type of the parameter.
Examples
Consider the following parameter declaration:
Since s is declared as a String, its default value must be a String. 15 isn't