[ASP.NET] Question about ScriptManager.RegisterStartupScript() parameters ?

Question :

protected void Button1_Click(object sender, EventArgs e)
{
ScriptManager.RegisterStartupScript(this, GetType(), "Popup", "successalert('Message 1');", true);
}

Using SweetAlert, about the third argument String of the ScriptManager.RegisterStartupScript() , besides the Popup, what other values can be set ? I didn't see the following URL?

ScriptManager.RegisterStartupScript Method
https://docs.microsoft.com/zh-tw/dotnet/api/system.web.ui.scriptmanager.registerstartupscript?f1url=https%3A%2F%2Fmsdn.microsoft.com%2Fquery%2Fdev15.query%3FappId%3DDev15IDEF1%26l%3DZH-TW%26k%3Dk(System.Web.UI.ScriptManager.RegisterStartupScript);k(TargetFrameworkMoniker-.NETFramework,Version%3Dv4.6.2);k(DevLang-csharp)%26rd%3Dtrue&view=netframework-4.7.1

Thank you very much.