Fix HFRL epoch boundary parsing

Previously, when generating reports, the code was only using HFRL data between the previous report and the current report, instead of going all the way back to the hfrl_epoch boundary. I have changed the index array from [0] to [-1] to grab the correct end of the boundary. I have also switched over the using the hfrl epoch reports instead of the sensing reports. We may want to revisit this logic, but this will work as long as the hfrl epoch is set properly along with the sensing epoch being set properly.