So what specifically does "devalue" mean in this case? Did he free up the markets to decide on the value of the money as the result of some policy change? I don't get it. Was there some sort of value cap established by treaty?

Now as I understand there is also a plan to keep doing this though, devaluing at like 2% per month. Which is still quite high. Pursuing a kind of chinese style export focused model where your cheap currency helps your exports look attractive, and some other effects.

I'm guessing that he wants to keep making exports cheap to sustain the industries long enough to repair them, but also knows that if he properly stops devaluing, he might actually get uncontrolled deflation. Which, although inevitable, you still want to try and limit.