On the effective range of DFAO

When I use DFAO, I find its display range is very small, only 100-200 meters range, beyond the scope of the object DFAO is no longer effective, but I can not find the option to adjust the range of DFAO, how can I adjust the scope of the impact of the DFAO?

I try to adjust the maximum occlusion option in skylight, but it does not control the display area of DFAO.