TX and RX are counting bites in and out. RX should be steadily incrementing when a GPS or other serial stream is feeding SkyView.
E/G/R describe some status information about the full sentences that are being received. E means error, but even when things are working normally and well you'll see some of those. G means good, well-formed sentences. This is the only one you should really care about - G should increment if GPS is being received and working properly. Don't worry about R, it's not useful.
