The translation I have says "from this night on, dew will whiten to frost" (although this version seems to be going for something more poetic than literal). The "look, a clue!" commentary was weird tbh but on the other hand, associating it with a holiday that would normally be spent with family adds to the loneliness of it, whether it was literally written then or not.
Re: 11. 月夜憶舍弟 Yuè-yè yì shè-dì