How to calculate 'compare' funtion in Matlab

I am studying RMSE and NRMSE according to ' https://en.wikipedia.org/wiki/Root-mean-square_deviation ' , ' https://www.mathworks.com/help/ident/ref/compare.html '

For example, I made like below.

Why is the NRMSE value different between NRMSE manually by wikipedia and NRMSE by compare code of MATLAB?

Could you teach me how to calculate 'compare' function mathmatically?

V1 = [11.5 7.6 6.7 8.3 7.7 7.4 6.5 5.6 6.6 11.2 11.9]; % obseved data
V2 = [11.9 10.8 8.3 9.6 11.4 10.2 12.4 9.6 8.3 8 9]; % estimationd data

RMSE = sqrt(mean((V1-V2).^2)); % RMSE = 3.14107

NRMSE = RMSE/(max(V2)-min(V2)) % NRMSE = 0.71

% to use compare
VV1 = iddata(V1', Vt');
VV2 = iddata(V2', Vt');
compare(VV1,VV2) % -48.46%
compare(VV1,VV2) % -116.8%