Wheel Circumference (mm) set for 29x2.0 CONTINENTAL DOUBLE FIGHTER 2.0

Much more accurate to roll out next to a tape measurer and get the actual number.  Mark a spot on the tire or use the valve stem and accurately measure.  I roll out three revolutions then divide by three to get more accuracy.  Keep a straight line right next to the tape measurer.  Convert to metric if needed.  Easy 5 minute job and it will be way more accurate than some charted number.

On top of that: I would engage sag throughout the measurement for suspension fork.

Yes, pushing down on handlebars does squish the tire and have some effect on the circumference.  I do push down to make more accurate, but at some point you're splitting hairs... are we measuring accurately whilst in the air/over bumps, wheel spinning but we're descending vertically?  When the fork is more lightly or more heavily loaded than static sag?  More tire compression due to sharp impacts of rocks and roots?  Lol.  At some point, close enough is close enough!  But your point is valid.

Yes, you are right and I knew that. . I repeat measurement after each front tyre pressure too. . And I am MTB rider. . But I somehow cannot help that.

Looks like ab. 10% off. It should be 2200+ for that tyre.

Really?  In all the time it takes to type all these posts you could just measure the actual circumference. 

Tools required:  Tape measurer and your eyes.  Done, then you have the real number.

After see meter: 2240мм for CONTINENTAL DOUBLE FIGHTER 2.0 29x2.0