Here's an interesting way to look at that question:
Consider some facts:
75,708 drops in a gallon
3 TBS sulfite in a gallon of sanitizer (assumed)
1 TBS = 3 tsp
You want 1/4 tsp in your 6 gallons of wine
1 TBS = 12 each 1/4 tsp
3 TBS in a gallon of sanitizer would contain 36 each 1/4 tsp
There are 36 each 1/4 tsp in 75,708 drops
Each drop contains .000476 of 1/4 tsp
You'd need 2101 drops to equal 1/4 tsp
2101 drops divided by 30 bottles in a carboy means you'd need to leave behind 70 drops of sanitizer in each bottle to equal the dosage of adding 1/4 tsp sulfite to a 6 gallon carboy
There are 20 drops in a ml, so you'd need to leave 3.5 ml of sanitizer behind in each bottle to equate to the 1/4 tsp for a 6 gallon carboy
Just fun food for thought.....................
I'm sure that
@sour_grapes will check my math / thought process.............