Gudeg is sweet for a reason. The jackfruit is stewed in coconut milk and gula jawa for six to eight hours, and by the end a 100g scoop is 127 calories with 22g of carbs, mostly sugar, and 5g of fat. It has almost no protein, under 2g per 100g. So the brown pile that looks like a vegetable dish is closer to a sweet stew.
Krecek is the red stuff on the side, and it is cow skin crackers rehydrated in coconut chili sauce. 50g is about 110 calories, mostly fat from the santan and the chili oil floating on top. Then areh, the thick white coconut cream, is 80 calories for a 40g spoon. Between gudeg, krecek and areh you have 320 calories before rice.
The dry Yogya style (gudeg kering) is more concentrated than the wet Solo style (gudeg basah). Kering has been cooked down longer so the same 100g scoop has more sugar and coconut, about 150 calories, while the wet version is closer to 110. If you are choosing, wet is lighter.
A Rp 15,000 to 25,000 plate at Wijilan or Mbarek gets you 650 calories with 95g of carbs and only 20g protein. Add ayam kampung opor and you are near 900, and that is the usual tourist order.