[Gretl-users] forecasting garch vol

http://www.mathworks.com/access/helpdesk/help/toolbox/garch/forecasting10... this data also in gretl you should do it open b-g garch 1 1; Y and i don't know how do i forecast.. forecasting future volatility...with mathlab. I am having trouble interpreting the output of garchpred,for example, spec = garchset('P',1,'Q',1,'TolCon',1e-6); garchfit(spec,bg); [coeff,errors,LLF,innovations,sigmas] = garchfit(bg); [sigmaForecast,meanForecast] = garchpred(coeff,bg,10); [sigmaForecast,meanForecast] VL = coeff.K/(1-coeff.ARCH-coeff.GARCH) newvar = sqrt(VL + (coeff.ARCH+coeff.GARCH)^[1 2 3 4 5 6 7 8 9 10]'*(sigmas(1974)^2-VL)) % this equation is refrenced Options, Future and other Derivatives 6th page 472 equation 19.13(JOHN C. HULL) sigmaForecast = 0.3834 0.3895 0.3953 0.4008 0.4060 0.4110 0.4156 0.4200 0.4242 0.4282 10]'*(sigmas(1974)^2-VL)) newvar = 0.3477 0.3559 0.3637 0.3710 0.3778 0.3843 0.3904 0.3961 0.4016 0.4067 why two result is different.. and during 10days volatility is mean(sigmaForecast ). is correct? i'm still in garch world -_-; anybody help me...