Values from GSR sensor

HI, I am trying to get the Human Resistance using this formula:
Human Resistance = ((1024+2*Serial_Port_Reading)*10000)/(512-Serial_Port_Reading)

I get is values like
(The right column is the resistor value and the left is the values from the GSR sensor)

When I am trying to use the formula on the sensor value I get 10 times smaller values Why?

Any kind of help will be thankful!<3<3<3