Your employer files a WC-1, a First Report of Injury, with your 40 hour wage on it. Does it have your actual wage on this form? Most likely not. The HR Department does not care to accurately pull your actual wages to enter on the WC-1 form. All they want to do is push the WC-1 form on to the insurance company for processing.
If you want your correct wages, you will need to pull your 13 weeks of wages prior to your injury and get this information to the claims adjuster as soon as possible. Then the adjuster will, by law, be required to re-do the WC-2 or WC-1 forms and then you could get a higher benefit rate of pay.