The pot is mostly water and silken tofu. A 200g block of soft tofu is about 110 calories, the egg cracked in is 70, and whatever seafood or minced pork the kitchen adds is 40 to 60. The rest of the 260 is the chili oil the broth is built on, which is the one ingredient that varies wildly between shops.
That chili oil matters more than people think. A kitchen that starts the pot with 2 tablespoons of gochu-gireum is adding about 240 calories before anything else goes in. Most lunch places use a lot less, which is why the average lands around 260, but a very red, glossy surface on the broth is a sign you are at the higher end.
The rice is the bigger lever. A 210g bowl is around 310 calories, more than the stew. Order the stew with half rice and you are at roughly 415 for a complete lunch with 20g of protein. The Gangneung-style versions with beef and extra fat listed by packaged brands run 450 to 475 per serving, closer to a full meal on their own.