The rice is not plain rice. It is cooked in coconut milk with turmeric, and it lands at about 160 calories per 100g against 130 for white rice. A stall scoop of 200g is 320 calories. FatSecret lists a smaller 150 calorie bowl, but that is a 100g lab portion, nobody gets served that at a warung.
The toppings are small but every one of them is fried or sweet. Kering tempe is tempe shreds fried and glazed in palm sugar, 75 calories for a spoon that weighs 30g. Serundeng is grated coconut toasted with sugar, 40 calories for 15g. Sliced telur dadar is 55 calories. None of them look like much on the plate, and together they are 170 calories.
The Manado version with cakalang (skipjack) and sambal roa is actually leaner than the Javanese one: the fish is grilled or shredded rather than fried, so the plate comes out around 560 calories with more protein. The tumpeng birthday version is the opposite, because the cone means more rice, often 300g, and the plate hits 800 without trying.
At Rp 12,000 to 20,000 this is a decent breakfast at 26g protein. The issue is it is 78g of carbs and most stalls pile the rice, so ask for less before they scoop.