Option 2: Stay quiet
Of course, you can still keep quiet. Especially if your partner revealed his number and the difference is considerable. If you tell the truth, you could face judgment from your partner, but if you lie, it will cost you one day.
Honesty is the best policy, and if you feel ashamed telling the truth, you can twist it a bit, especially if you think it is beneficial for your relationship. But, on the other hand, if a lie is your choice, do it as quickly as possible.
Once you have lied, remember the number you said.
It’s important to say that any successful relationship is based on honesty and being able to have a genuine conversation. If you cannot talk openly with your partner about everything, including your exes, maybe you should find your happiness elsewhere.