Hitbox is usually a hack used to increase the size of an entity's hitbox meaning you can hit the target with less accuracy needed. However, don't worry as our anti-cheat commonly kicks people even though they are playing fair and square. There is normally a trigger to set the anti cheat off but I wouldn't bee too sure about what that is exactly. If it is consistently kicking you then I advise you to contact a SA, however if it is a one off then you should be fine. Hope this helps :)