It's gonna vary based on your fertilizer, the strain you're growing, and the stage of growth your plant is in. The "quarter to a half" rule is basically just a guideline to get people in a good ballpark so they don't overdo it. Fertilizer companies tend to recommend pretty high dosage so you buy more often. I use General Hydroponics(Terra Aquatica) and typically run my nutrients at half strength to their recommend dosage with good results.