In cases of temporary total or temporary partial disability no compensation is allowed for the three calendar days after the disability commenced, except as provided by section 176.135, nor in any case unless the employer has actual knowledge of the injury or is notified thereof within the period specified in section 176.141. If the disability continues for ten calendar days or longer, the compensation is computed from the commencement of the disability. Disability is deemed to commence on the first calendar day or fraction of a calendar day that the employee is unable to work.