I took a pg test one line was super dark and the other was very vague what does this mean?

The darker line is the control line... the other, if read within the time required for an accurate result stated on the directions is possibly a positive result. If it was read later it may be an evaporation line.
Would be a good idea to try another test to see if you get similar results. Might want to wait a few days and see if a darker line appears.