I do not measure exactly when I feed my start. It ends up being about a 1:4:4 ratio, and works great for what I do!
Here is my method:
Take about 1/4 cup of your discard and add it to a jar. Add about 1 cup flour and 1 cup water and stir until there is no more dry flour. The texture should be like thick pancake batter, or like sticky frosting. The remaining discard can be used to make pancakes, banana bread, or stored in the fridge for another time.
Your start is 'fed' and 'active' when it is about doubled in volume and it is airy and full of bubbles. This can take anywhere from 4-12 hours. It will be ready much faster in the summer, and take longer in the winter. If I need it sooner in the winter, I just put it in the warmest area of my home.
You can do the float test to see if it is ready: add 1 teaspoon of fed start to a cup of cool water. If it floats, you can use it!