I'm picturing raw broccoli - stiff cell walls and fairly watery - that is, containing water. Then I picture cooked broccoli. The cell walls, as they cook, soften and collapse. Some of the water (which is not calorie-dense) leaks out as it cooks. The broccoli collapses in on itself. You put stiff raw broccoli florets in a cup measure, and there will be less calories than when you put the collapsed, more compact cooked broccoli in the same cup measure. So that explains, for me, why cooked broccoli has more calories, per cup,than raw broccoli.
The same explanation would apply to cooked lettuce, 1 cup, vs. raw lettuce, 1 cup!