I’m really not sure where all of these 1/8 and 1/16 tsp per racking are coming from, but let’s set the record straight.
Sulfite levels should be maintained to protect wine from both oxidation and organic invaders. The minimum sulfite levels are a function of the pH and color of the wine, the lower the pH, the less sulfite it takes, and visa versa. White wine needs more sulfite than red.
Sulfite gets “used up” in wine as it scavenges oxygen and protects your wine, some becomes “bound” and some gets used up, it’s why we have to maintain sulfite levels, and how fast it gets used is based on the wine itself and how you handle it.
Properly administered sulfite protocol says that sulfite levels should be checked on a regular basis, and adjusted as needed to maintain adequate levels of protection. Not everyone is willing to invest the money and time to do this testing.
This is where the “rule of thumb” has been applied, which is to use 1/4 tsp of potassium metabisulfite, per 6 gallons of wine, every three months. This doesn’t work for wines in barrels, which may require more frequent application. One doesn’t need to add sulfite at every racking, every three months is fine unless you expose your wine to excessive amounts of oxygen.
If you want to maintain your sulfite levels as low as possible, invest the time and money into the testing equipment, and you’re off to the races. I wouldn’t advise that anyone summarily cut their dosage from 1/4 tsp / 6 gallons / 3 months down to 1/16 tsp without testing. Just my opinion.