Sill question, but does anyone know what the codes at the bottom left of your boarding pass mean?

I was sifting through mine and spotted a few different ones like: 76, ==, 00, 8I, U4, JV, GV, 4Q, 6V, lJ, H4, PS, IL, ML, TL, TC, C3, and $$ , etc..

Your wisdom and expertise would be greatly appreciated on this matter