That is the time in which the program will air.
In addition, the first number is always the time zone you're in, while the second number represents the timezone before yours.
Therefore, in this example you are in the Eastern Time Zone.
If the example is 8/7c. Then the program airs at 8 o'clock Eastern and 7 o'clock Central.
The reason both timezones are represented like this is due to areas within the viewing audience which border timezones.
To ensure that viewers in both timezones get the most accurate information in the easiest most cost effective means; they simply present both timezones.