Sup sayur bening is as simple as it sounds: clear broth, aromatics like garlic and onion, then cabbage, carrot and tomato. No coconut milk, no heavy rempah. The 60 calories for a full 320g bowl is genuinely that low because vegetables are mostly water and fibre. The 15-calorie broth and about 8 calories from the minimal oil in the base are actually doing more numerical heavy lifting than the vegetables themselves. To be honest, these numbers are a ballpark estimate because solid lab data for this dish is thin. Kedai to kedai will vary, and some hawkers are heavier-handed with oil than others, but 60 to 80 calories is a reasonable range for the plain version.
What actually moves the maths here is what gets added. Stay plain and you are at 60 calories. Throw in 60g of soft tofu and you are at 100. Ask for chicken and you are up to about 120. Add 30g of cooked vermicelli and you are at about 95, which now makes it a light noodle soup instead. The oil in the base is already minimal at 1g and 8 calories, but if you are at a stall that fries the aromatics more generously, you could creep toward 80 or 90 calories before any protein is added. Order it plain with rice on the side and you have basically used your soup allocation for nothing.