I would think "no activity" means no work. If this is due to an accident at work, then you should contact your employer or the claims adjuster and make sure this out of work note from the doctor is forwarded to the insurer. I don' t practice law in your state but I have practiced WC Law in Virginia for 35 years.
This response is meant to be information only and should not be considered to be legal advice. This information is not meant and should not be construed to be the formation of an attorney client relationship. I practice Virginia Workers compensation law and Social Security Disability law.
Were you hurt on the job? If so you need to contact an attorney who handles workers' compensation in MI. In GA if you are hurt on the job and an authorized company physician takes you off work for more than 21 days straight then you are entitled to workers' compensation benefits.