The isotope proportional composition of the sample used must be measured and taken into account.
From the en.wikipedia.org
The width of the notches is proportional to the interquartile range of the sample and inversely proportional to the square root of the size of the sample.
From the en.wikipedia.org
Another interesting facet of the technique is that, unlike conventional NMR, the signal response is proportional to the sample length, but not its volume.
From the sciencedaily.com
The gas then pushes red ink along tiny channels on the device, with distances being proportional to the amount of biomarker in the sample.