Why does the Firewall app be on top of the data usage chart?
The Firewall app uses your device's VPN service to operate efficiently. As a result, all incoming and outgoing data traffic is routed through the Firewall's VPN.
Unfortunately, the way that Android's operating system attributes data usage can be misleading, and this results in the Firewall app appearing at the top of the data usage chart. While it may appear that the Firewall app is using all of your data, this is not the case.
The Firewall app is simply acting as a conduit for your data, and it is not actually consuming any more data than usual.