The collimator and camera are ideal (aberration-free), and the dispersers are plane.
The numbers are measured by tracing rays through the vector grating equation and Snell's law, from the slit to the detector; the closed forms of the design notes (R φ = 2 tan δ W/D in Littrow, Fcam ≥ npix p/(φ D), and the rest) are reproduced by the trace and checked in the validation suite.
The resolving power is the FWHM of the slit image, with the grating's diffraction limit and the pixel width added in quadrature; blaze efficiency is the scalar sinc² envelope, relative to the peak.
Presets come from the instrument papers and manuals. The presets are approximate and are meant to reproduce the optical design of each spectrograph (and so the numbers); the drawing's spacings, folds, and angles do not follow the actual optical layout. Fiber-fed instruments are entered as the slit of equal line width.