Unfortunately in these borderline cases the only way to know for sure is to wait a few days and try again or set up a doctor's appt to get a better test.
In Germany, for example, for abortion (without medical indication) to be penalty-free you have to have a so called "pregnancy conflict counselling session" and the doctor's appointment all within a certain timespan. Now during covid, many of those doctors and the counselling services did not operate or only in a diminished capacity.
Those few days are nothing to sneer at.
Of course, another solution would be better/non-penalized access to these services and better preventative health care. But we're getting nowhere by just pointing at root causes without the radical action to change them.
The fact that the site provides on-line tools to change contrast, etc., is telling in itself.
But here are direct comparisons between an analog an digital ones:
* https://www.countdowntopregnancy.com/pregnancy-test-gallery/...
* https://www.countdowntopregnancy.com/pregnancy-test-gallery/...
* https://www.countdowntopregnancy.com/pregnancy-test-gallery/...
* https://www.countdowntopregnancy.com/pregnancy-test-gallery/...
The comments are very interesting and you should take a peek. Helpful commenters are using image editing tools to check out whether the second line is actually there or just imagined.
A second stripe means a life-altering situation and with regards to access to terminations, time is very much of the essence.