Look like you are trying to cast a date value to an integer
Considering the 'Reminder Date' in addDays('1899-12-30', int ('Reminder Date')) is a value like '1899-12-30' or 26/10/2022 you will get this error:
"InvalidTemplate. Unable to process template language expressions in action 'Compose' inputs at line '0' and column '0': 'The template language function 'int' was invoked with a parameter that is not valid. The value cannot be converted to the target type.'."
if that value is an integer, like addDays('1899-12-30', int ('1')), it would work
If you share what you are trying to accomplish, I may be able to help.