|Description||Optional parameter used for creating a subscription. Represents the amount of the first installments of the recurring payment.
The number of these first installments is defined by the vads_sub_init_amount_number parameter.
This amount is presented in the currency defined by the vads_sub_currency parameter and is expressed in its smallest unit .
The value may be empty but cannot be negative or equal to 0.
Input and output field, returned in the response (IPN and Return URL).