By matching with standers, the peak areas give the percentage of fatty acid esters

Fatty acid methyl esters (FAMEs) are identified by comparing the retention times of the chromatographic peaks with those obtained with the methyl esters from a mixture prepared with fatty acids from a reference standard supplier. The structural assignment is confirmed by comparing their mass spectra with those of reference standards. The weight percentages of fatty acids are then approximated by the area.

Hi

The calculation and processing protocols are well explained in the following paper

https://doi.org/10.1007/s12161-021-02203-0

I hope this helps!