I read it as just telling us that 40k moths per day at 1/2 calorie each = 20k calories. They just did that math for us. Beyond that, they carelessly omitted the

I read it as just telling us that 40k moths per day at 1/2 calorie each = 20k calories. They just did that math for us. Beyond that, they carelessly omitted the info about how the 40k number was estimated. But I'm not sure. Definitely unclear mediocre writing in that sense.