这个算出来的annualized volatility不是很明白。

No.PZ2016062402000047 (选择题)来源: Handbook

A risk manager estimates daily variance htht​ using a GARCH model on daily return rt:ht=α0 +α1rt−12+βht−1, with α0=0.005,α1 =0.04,β=0.94rt​:ht​=α0​+α1​rt−12​+βht−1​,withα0​=0.005,α1​=0.04,β=0.94.

The long-run annualized volatility is approximately

The long-run mean variance is h=α01−α1−β=0.0051−0.04−0.94=0.25h=1−α1​−βα0​​=1−0.04−0.940.005​=0.25. Taking the square root, this gives 0.5 for daily volatility. Multiplying by 252252​, we have an annualized volatility of 7.937%.

请问这道题的daily volatility算出来都是0.5 （50%）了，为什么乘以根号250算出来的annualized volativity只有7.937%，题目也没说这个0.5应该是带百分号的。 求解惑。