Well, I am assuming, due to the way you wrote it, that you mean 20 hours on and 4 hours off.
I am basing my answer on a friend's experience, because I do not grow autos, but I have watched him struggle.
He has done the same thing many times, trying to grow reg fems at the same time as autos.
It always slows them down and he gets very little from his plants as a result.
The times I have seen him put it on 12/12 and let it go, he has done much better.
EVen autos can be susceptible to photoperiod manipulation, and switching light periods confuses the plant.
I would give it a hard direction to bloom, by putting it back to 12/12/
Is that the right thing to do?
Man, I don't know. Autos bring some traits to plants that are not visible, so it's hard to know what you are dealing with.
But giving it a signal that it's spring again might not be the best idea... the 11 weeks may start over and the plant will never finish before you cut it...
I would treat it like a reg now. I would send it a strong signal and force it to finish.
It's up to you to decide what to do.
If you could ask the breeder, he could give you directions focused on that specific strain...