Error correction forumla

Dear all.

I am trying to measure the Current through CT.when i measure the value with current and without current flow it shows min current.i would like to display zero current without changing equation.if no current flow it should show zero else it should normally.

is there any error correction formula for such application

https://www.the-diy-life.com/simple-arduino-home-energy-meter/

Have you tried subtracting the value you get when you try to measure with zero current?