If your toothbrush has already been paired with another device, a message will appear: "This brush is already paired with…: do you want to change the settings and pair this toothbrush with your profile? (Warning: the old connection will be lost")
If you select "yes", the old profile will no longer be associated with this toothbrush: it will be replaced by the new profile instead. If you answer "No" you can only use your toothbrush with your profile on a restricted setting.