Android Question Firebase Messaging send to specific user

Private Sub SendMessage(Topic As String, Title As String, Body As String) As ResumableSub
    Dim Job As HttpJob
    Job.Initialize("", Me)
    Dim data As Map = CreateMap("title": Title, "body": Body)
    Dim message As Map = CreateMap("token": Topic, "data": data)
    If Topic.StartsWith("ios_") Then
        'B4i
        Dim Badge As Int = 0
        Dim iosalert As Map =  CreateMap("title": Title, "body": Body)
        message.Put("notification", iosalert)
        message.Put("apns", CreateMap("headers": _
            CreateMap("apns-priority": "10"), _
            "payload": CreateMap("aps": CreateMap("sound":"default", "badge": Badge))))
    Else
        'B4A
        message.Put("android", CreateMap("priority": "high"))
    End If
    Dim jg As JSONGenerator
    jg.Initialize(CreateMap("message": message))
    Log(jg.ToPrettyString(4))
    Job.PostString($"https://fcm.googleapis.com/v1/projects/${ProjectId}/messages:send"$, jg.ToString)
    Job.GetRequest.SetContentType("application/json;charset=UTF-8")
    Job.GetRequest.SetHeader("Authorization", "Bearer " & Token)
    Wait For (Job) JobDone(Job As HttpJob)
    If Job.Success Then
        Log(Job.GetString)
    End If
    Job.Release
    Return True
End Sub