I believe you were only partly correct. You are correct that we are not employees of Amazon. However, Amazon has set a limit of up to 40 hours per week that each independent contractor may work. If you check your availability settings and set all of them for Max availability, you will notice that Amazon has a section stating that you are willing to work up to 40 hours per week. Just as they are able to set the pay rate, they are able to also set the maximum hours that an independent contractor may work with their company per week.