@dor123 , have you tried the spectrometer with single wavelength light sources? See if the reading on the spectrometer matches with the actual wavelength. For example, a red laser is ~650nm, a green laser is ~532nm, a violet laser is ~405nm, a neon lamp has a peak at 632.8nm. If the values for these are close (+ or - a few nm) then the spectrometer should be correct.
(Don't point the laser directly on the spectrometer, point the lasers on a white wall and place the spectrometer pointed towards the wall looking at the laser dot.)