Depends on your goals. But usually with IF, you’re not suppose to compensate for the meal you don’t eat.
You’re supposed to eat mindfully to satiety during your meal(s) and if you find the resulting calorie intake too low (e.g: let’s say your TDEE is 2400, but you can’t eat more than 600 calories in a single sitting), you should consider increasing your feasting window and fit a snack and/or another meal.
Eat til satisfied and full. When trying to cram it all in an hour you will naturally keep calories in check. This is assuming you’re eating real food and not tons of processed stuff, sugar, etc. Because the bad stuff won’t fill you in the same way.
When I first started with 16:8 I was doing about 1800. With OMAD I get full around 1200-1500 usually, depends what the food is. But I’m not counting per say, just logging what I eat because I like all the data. There were a few days I could hit 1700ish, other days after 1000 I was just done.
I eat a normal sized meal. Usually trying to avoid sugar and simple carbs. So far I’ve been doing OMAD about two months with 48’s and more. I’m still trying to figure out what meals work best. Best part is continually loosing weight. Eat till you are satisfied. Don’t overeat