That is a great question, BRUCEFL56. The only data that goes against your 500MB is the data that goes through the Verizon Wireless network. If you're on Wi-Fi for the data that goes over the local area network. With that said, many devices have a setting that allows you to use LTE and Wi-Fi simultaneously, which you will want to disable if you only have 500MB of data.
PeterP_VZW