I would class that as a positive, I've had all sorts - evaps, fainter than that, ones like that, darker than that etc!
I have had so many as I go a BFP and just kept testing last time! I literally used 20 tests! The lines all varied, even on the same brand ones with the same wee! As they say, a line is a line (or at least it is when it's not an evap!)
If you use first morning wee, it will be way darker tomorrow. I did the same thing last time and I lasted until 3:45am and tested, lo and behold, it was a "pregnant" on a digi and a darker line on the Asda test. I think I was only 10 or 11 DPO. What are you again? Xx