Using the lines that you have both read and white values:
Divide the red by the white:
16 / 10 = 1.6
40 / 25 = 1.6
The scale factor is 1.6.
So you have 1.6 L red paint / L white paint
Now multiply the amount of white paint by 1.6 to find the amount of red paint:
4 x 1.6 = 6.4
13 x 1.6 = 20.8
20 x 1.6 = 32
