So he deliberately told Alice what he witness she was capable of. So that he could see what reaction she will have and what she was going to do to him.
He's saying these words because he wanted to test her.
And see what her goal is.
Lance seriously looked at her before uttering the words, "My goal is to infiltrate the fortress and take back the things they owe me." He sharply look at her. "But it's impossible to do it alone. At least, with my current strength, I will be walking into a trap. That's why I need you."
With this, Alice raised a brow. "Why do you think I should help you? What you want to do is equivalent to betraying the fortress."