Kaz, I had a day like that yesterday, ended with about 650-700. It slows things a bit but still works. I’ve lost over a pound since Sunday. If I realise I’m going to end up over target cals eg because I’m too hungry to manage, I try to have protein and fat, not carbs, as that’s more satisfying so I won’t go far over, and it won’t raise my blood sugar and insulin so much (fat is important for that as lean protein eg chicken will raise insulin). So maybe a small boiled egg (74 cals) or some hot milk (half a cup, 73 cals) mixed with hot water, very satisfying, or similar of almond milk, 30 cals. The egg is better as there is some carb in the milks, but sometimes they are more satisfying psychologically in the evening. Or soup, as Cinque says.

I also try, on the day after I’ve gone over, not to eat till lunch time, which just extends the fast day a bit. But that may not suit you.