Different sample amounts have different math correction factors attached to them.
For example, if you are using .10 Normal NaOH reagent and taking a 3 ML sample, the math correction factor is .25. (See Presque Isle test instructions).
Whereas, if you are taking a 5 ML sample and using the same strength reagent, you would use a .15 factor to arrive at TA%. (See Crosbey & Baker test instructions).
A 10 ML sample of the same strength reagent (0.10N) would require that a math correction factor of .075 be applied.
There is no logical progression, there just appears to be one. In fact if "x" is the math factor you seek, then when you solve the equation for "x", the formula is:
"X" = NaOH strenght X 7500 divided by 1000 X the sample size.
Applying this formula, the solutions for "X" (the math factors used to arrive at TA%) are as below:
At 1 ml, use .750, 2 ml use .375. 3 ml use .250, 4 ml's use .1875,
5 ml's use .150, 6 ml's use .125, 7 ml's use .1071428, 8 ml's use .09375, 9 ml's use .083333, and at 10 ml's use .075.