Default value: Our app will apply the value which is provided in the file. If the value is blank then our app will fill the information which you provide in the Value box.
Override: Our app will ignore the value which is provided in the file and it will fill the information which you provide in the value box.
Blank value: The value box won't be available. Our app will upload the data as it is provided in the file.
Merge & Expression: You can merge two field's values into one QB field. or you can add free text with the column values. The only constraint is that the mentioned columns cannot be used in other mappings.
Syntax: {COLUMN_NAME_1} {COLUMN_NAME_2}
Examples:
1) {FIRST_NAME} {LAST_NAME}
2) Stripe Customer {FIRST_NAME}