The SCS values used for the calculations are taken from [1,2]. Both papers contain a much finer division of functional groups, e.g. different SCS values are given for conjugated and non-conjugated compounds. However, an exhaustive list would become unmanageable so only a subset is used here. In most cases the loss of accuracy is not great.
Since values for the 1H increments of several groups are missing in  they are approximated using similar substituents.
Carboxylic acids and esters are approximated by increments for ketones/aldehydes
Alkynes are approximated with increments for cyano compounds (nitriles)
Literature "New parameters for prediction 1H NMR chemical shifts of protons attached to carbon atoms"
Bürgin Schaller R, Arnold C, Pretsch E Anal. Chem. Acta 312 (1995) 95-105
 "Parameter set for the prediction of the 13C-NMR chemical shifts of sp2- and sp-hybridized carbon atoms in organic compounds"
Pretsch E, Fürst A, Robien W Anal. Chim. Acta 248 (1991) 415-428