Yes, it counts as long as you can prove it falls under TEER 0,1, 2 or 3. The staffing agency has to provide all the details for the company that you worked for along with the job description. Better ask your staffing agency to also include the NOC code on your letter along with the job description. Even if they don't mention the NOC it's still ok as long as it matches and aligns with the TEER classifications mentioned above. Additionally, include all your paystubs while submitting your application along with the work experience letter.