Digital Broadcast Tv stations have REAL and Virtual Tv Channels.
A REAL Digital Tv Channel is what is being transmitted and received.
A Virtual Channel of most cases is the Legacy Analog Channel -'number'- from the time when the Tv station was transmitting analog signal.
During and after the digital Tv transisition many Tv stations choose to keep the analog channel number even though the Tv stations REAL Channel is different.
Example , Analog channel 4 is what was transmitted before the transisition and now the station is transmitting on REAL Digital Channel 15.
It is important to know the REAL channel number so as to select the Correct antenna.
Tvfool shows both the REAL channel number and the Virtual channel number in the tvfool radar plot report.