I suspect achoo is referring to the fact that most trainers are easier to pedal than a bike on a real-world road. So your speed and distance numbers tend to be higher on the trainer than they would on a real-world ride. You can compare one trainer ride to the next, but it would be a mistake to try to compare trainer rides to real-world rides. For best results, you'd ignore the speed and distance information while riding on the trainer and instead focus on heart rate, power output (if you have a power meter) and the duration of exercise.