For the Activity-based method, users should input the 'Amount' data, which is a required field for accurate emission calculations. In this method, the system necessitates the amount for emission computation, making it a mandatory entry. On the other hand, entering the 'Cost' is optional. While users can include cost details, the specified amount is the primary and essential input for emission calculation under the activity-based method. Therefore, for this method, it is crucial to prioritize entering the amount to ensure a precise evaluation of emissions, with the cost being an optional supplementary input.