How to assume on Twitch subs?

At streamers like Monte there are people who give subs away.

Then there's always a display that the person is giving this away and there's always a time. I hope you all know what I mean.

My question is, how can I assume that I can also become a sub because there's always after the overlay that the person has become sub.

You can't assume that is random, so someone gets the sub.

Yes, but why is it then shown to me that it says that the person is giving away subs and that it still has time, for example you have 6 seconds.

Ah I already know what you mean thanks thank you