MTN Nigeria is increasing the number of digits for the PINS on recharge vouchers from 16 to 17 digits. This means that when you purchase a scratch card of any denomination, the number of PINs you will type in the process of loading will be 17.
Despite the change the old 16 digit vouchers remain valid and useable. Also, whether you recharge a 16 or 17 digit pin code the value of the airtime remains the same.