Is this a glitch?

I sent a follow request to someone I know on instagram. After few hours I got notification that they have accepted my request. I did not get the notification that they have started following me however when I checked my followers it shows that they are following me and when I checked their following it shows that they are following me. So does this mean that person is following me or not? Why did I not get the notification? Because last week also I sent a follow request to someone else that time I got two notifications one that they accepted my follow request and second that they have started following me.