Theoretical precision limits for stellar label determination from LAMOST of hot stars, expressed through the CR bound, (Eq. (3)), for a fiducial B star with T_eff = 18 000 K, log g = 4.0, [Fe/H] = 0, and vsin i = 100 km s⁻¹. The LSF and S/N of the Kurucz model spectra as a function of wavelength are matched to that of a LAMOST B star spectrum, with S /N = 100 at 4650 Å. The CR bound is expected to vary by 1/(S/N). The units of the CR bound on the y axis differ from label to label: they are 1000 K for T_eff, cm s⁻² for log g, km s⁻¹ for v_mic and vsin i, and dex for abundance [X/H], except for He. For He, the number indicates the atomic number ratio N_He/N_tot. Labels shown in red are those we attempt to derive from the LAMOST spectra in this work.