The analog input range is set by the Vcc. If the chip is a 3.3V processor then your range is 0 to 3.3V. If it is a 5V version then your range is 0 to 5V. The resolution is set by the AnalogReference statement.
On a 5V board the default is 5V on 5V boards and 3.3V on 3.3V boards. You can change it to Internal with this statement making it 1.1V but then your allowable range is 0 to 1.1V and no higher.
You have no optioins here . You have to use 5V, so you can measure anything from 0 to 5V and the value measured is
5V/1023-0.00488V (4.88mV) per count so anything you measure is (Vanalogin/0.00488V) counts.
1V=204 counts
2V = 408 counts
3V =612 counts
4V= 816 counts
5V = 1023 counts