My experience is pay attention to the manufactures suggestion and adjust off of it. Pay attention to what the surface you're trying to clean is and what you're trying to clean off it (type and amount). Start conservative and work up, being careful about what your risk is. On high risk areas (or difficult/expensive to fix), be careful about going past manufactures recommendations (or even at recommendation over multiple uses).
When using a cleaner new to you, I would work up from low risk areas/cars while I learn the cleaner. WATCH FOR HARSHNESS. You don't want to have to try bringing an interior back from a harsh cleaner.
If it says 1:20, I would start at 1:50 on any interior. And, that would be on an older, average priced commuter car.