:deep doesn's work when use :nth-child selector

[sdutwsl]

When I use

        :deep(.manage-atcs-item span:first-child){
            flex: 1 1 1;
        }

It returns

        .manage-atcs-item span:first-child {
            flex: 1 1 1;
        }

But when I write

        :deep(.manage-atcs-item span:nth-child(1)){
            flex: 1 1 1;
        }

It returns

        .manage-atcs-item span:nth-child(1).l-612139 {
            flex: 1 1 1;
        }

The version of stylers I use is 0.3.2, and leptos 0.6.12.