One medium bakso is about 57 calories, and 60% of that is fat, not beef. Cart bakso is beef mixed with tapioca flour and fat, which is why it is bouncy and cheap. Five meatballs is about 285 calories and 17g protein. A bowl of 'bakso 10' at Rp 15,000 is easy to find and it doubles the count.
The rest of the bowl is smaller than people assume. Mie kuning 50g is 70, bihun 30g is 35, one tahu is 40 and the clear broth is 40 if it is not too oily. So a standard bowl is 480 and the meatballs are 60% of it. This is why bakso without noodles (bakso kuah only) at 340 is a decent protein snack.
The extras change everything. Bakso urat (tendon) is bigger, about 90 calories each. Bakso telur has a whole egg inside, about 130. Bakso jumbo or bakso beranak is a 150g ball with smaller ones inside, 300 calories on its own. A bakso Malang bowl with pangsit goreng, siomay and tahu goreng is around 620.
Then the sauce. People pour in kecap manis (25 calories per tablespoon) and sambal (often chili in oil, 40 per tablespoon) until the soup goes brown. Two spoons each and that is 130 calories added to what was a clear soup.