My response is -- in hindsight -- confusing. Let me explain better.
Draw an 8 oz sample, add sugar, taste. The overall volume of the sample is reduced by the amount of wine tasted. Repeat this several times and the wine / sugar ratio is altered so the actual wine volume is less. For example:
round 1 - 8.0 oz wine, 5 ml sugar, 1/2 oz removed to taste
round 2 - 7.5 oz wine, total 10 ml sugar, 1/2 oz removed to taste
round 3 - 7.0 oz wine, total 15 ml sugar, 1/2 oz removed to taste
round 4 - 6.5 oz wine, total 20 ml sugar, 1/2 oz removed to taste
round 5 - 6.0 oz wine, total 25 mi sugar, 1/2 oz removed to taste
The problem is that by round 5, the calculation is to add 25 ml to 8 oz of wine, while the taste test is adding to ~6 oz wine. This is not exact as the amount of sugar is reduced by each tasted sample, but it illustrates the situation.
This should produce a less-sweet wine, but somehow I managed to mess up the calculation once and over-sweetened. Nope, no clue what I did other than having a problem performing simple multiplication.
Are you doing something different?