How accurate is this count?

Hi! I’ve been trying to lose weight on and off for ages and having problems. Been at my heaviest a while now so doing everything I can yet I cant seem to find answers to how many calories im burning on a treadmill ANYWHERE to accuracy, so i resorted to chat GPT and it told me 500-570. I asked it as a 5’11 120kg female, how many calories would i burn on a treadmill for 30 minutes at 3mph on a 7% incline. The machine itself read 150, but of course, thats not tailored to me whatsoever its just general. 500-570 seems steep.. Tia!