faint positive or evap line...how do u know

im having a lot of trouble with a test i took. it is hard to capture it on my camera but there is a line...but is it a faint pos or an evap line? it took about five minuted for the test window line to fully develop and then 10 minutes later another line showed up...but its super faint and i have no clue if its a positive or not. how do u tell the difference?