why does channel x show up on my dtv as channel y

normx004

Estimable
Feb 20, 2014
2
0
4,510
specifically, my daughter was happily watching NBC (with her DTV and powered antenna - no cable) on channel 15-1 in Madison, when it disappeared. After trying various things I called the station and an engineer told me "well, we actually broadcast on channel 19 but the tv translates/changes that to channel 15"...and after i tuned the TV to 19, there was NBC.

what is going on with this translation of the channel numbers?