I bill per week, but I keep track of my hours to the minute to be fair with my customers. My customers only get the number of days I have been working on an ite

I bill per week, but I keep track of my hours to the minute to be fair with my customers. My customers only get the number of days I have been working on an item, the exact number of minutes making a day is my own cooking. The cooking is that, I can only get 5h to 6h of highly focused work per working day "over the year". Sometimes, even if I recorded some hours for the customers, when I consider them not well spent, I just remove them from my logs. The goal is always to make my customers happy. I have been doing it like that for the past 15 years, the customers keep coming, so I suppose it works well.