The rules section on National Will does not make it clear whether the calculation each turn is cumulative or does it reset to zero each time. I am assuming it resets to zero at the beginning of each calculation.
FWIW I believe this is covered in 11.0:
Add up the number of markers in the Victories box. From that value, subtract the number of markers in the Defeats box, the number of ethnicities in Revolt, and the number of Strategic Sites controlled by the Allies (see 7.7) at that moment. Ignore markers in the Stalemate box. Place the National Will marker in the corresponding box on the Austro-Hungarian National Will track
"The corresponding box" in which you place the marker is the box with the number which you just calculated (i.e. victories - defeats - revolts - strategic sites controlled by allies).
(For the alternate (cumulative) interpretation, I'd expect other wording, e.g. "move the marker that many spaces from its current box" or some such.)