The milky colour fools people. That white comes from bone collagen and emulsified marrow fat, and a 500ml bowl of broth is about 170 calories. Not nothing, but not cream either. The 70g of sliced brisket is 150 and the small tangle of somyeon noodles at the bottom is about 80. That is your 425.
Then the rice arrives. Almost everyone in a seolleongtang house tips the whole 210g bowl into the soup, and that is the moment it goes from 425 to 735. If you are trying to keep the number down, tip half in and leave the rest. The soup is 650g on its own and nobody leaves hungry.
Watch the salt. The broth is unseasoned when it lands, and the standard move is a heaped teaspoon of salt plus a big scoop of kkakdugi juice. That is where the 1,500mg of sodium comes from, not the kitchen. Season lightly, eat the kkakdugi rather than pouring its brine in, and you fix most of the problem for free.