Faint line? What do you think?

Karizma

I’m a few dpo not sure exactly maybe a week but I took this and laid it flat for 4 minutes and came back to it and immediately took pictures this is how it looked when I flipped it over what should I do? Retest? Is it evap? Doesn’t evap have no color? I can see the rain line going all the way down in person but only the top has dark color