The stew itself is 244 calories for a full 400g pot. That is less than a bowl of rice. Old kimchi has almost nothing in it, the tofu is 60 to 70 calories, and the broth is mostly water and gochugaru. The pork belly is the only heavy thing in the pot, around 165 calories for the 50g most lunch places put in. If the cook is generous with belly, you can add another 100.
The 555 figure assumes one bowl of rice, about 210g. Most 8,000 to 9,000 won lunch sets give you free rice refills, and a second bowl takes you to 865 before you touch the banchan. The gyeran-mari or fish cake on the side is another 80 to 150. It is easy to walk out of a kimchi jjigae lunch at 900 calories while thinking you ate soup.
Tuna kimchi jjigae runs lower, around 104 calories per 200g portion according to FatSecret Korea, because canned tuna in water has a fraction of the fat of belly. Budae-style versions with spam and ramyeon added are a different dish entirely and can double the number. Ask what is in the pot before you assume it is the light option.