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Community Moderator Alumni are previous members of the Moderation Team, which ensures conversations are friendly, factual, and on-topic. Moderators are here to answer questions, escalate bugs, and make sure your voice is heard by the larger Fitbit team. Learn more
@Wendyjo407 Welcome to the Fitbit family! Have you double checked on your profile if your personal data is correct?
If it is, then this is probably happening because the weight, age, and height are not the same as yours. Even if it is just a small difference. Because they are different, the BMR (Basal Metabolic Rate) is different too. I think those extra 100 calories they burn is because of the BMR. Check this article for more details on this.
However, if you feel that your watch is under counting calories, please perform a restart on it. That should help you out.
Keep me posted! 
Best Answer
Community Moderator Alumni are previous members of the Moderation Team, which ensures conversations are friendly, factual, and on-topic. Moderators are here to answer questions, escalate bugs, and make sure your voice is heard by the larger Fitbit team. Learn more
@Wendyjo407 Welcome to the Fitbit family! Have you double checked on your profile if your personal data is correct?
If it is, then this is probably happening because the weight, age, and height are not the same as yours. Even if it is just a small difference. Because they are different, the BMR (Basal Metabolic Rate) is different too. I think those extra 100 calories they burn is because of the BMR. Check this article for more details on this.
However, if you feel that your watch is under counting calories, please perform a restart on it. That should help you out.
Keep me posted!
Best Answer