The ISR 4331 router has 3 interfaces as stock and they start numbering at 0.
GigabitEthernet0/0/0 - Can either use the 1000base-T port or the corresponding SFP port
GigabitEthernet0/0/1 - Is only a 1000Base-T interface
GigabitEthernet0/0/2 - is only and SFP interface