There is nothing magic about "getting to 15 drops..."
The amount of Miracle-Mineral-Supplement taken should be related to your body weight. Dr. Hesselink states using 1 mg of activated sodium chlorite per kg of body weight.
For your weight, you should be at 5 drops and work up to a maximum of about 10 drops if you want to shock your system.
Since drops are a bit variable as a measuring system, 5 drops is about 0.294 ml and 10 drops is about 0.588 ml of Miracle-Mineral-Supplement . Since fractional ml measurements are difficult to measure, I would suggest adjusting the strength of your sodium chlorite solution to allow for easy measurements.
For example, if you adjust your sodium chlorite solution to a 5% solution, you would then be looking at using 3 ml and 6 ml. This would be much easier to measure.