Walmart cheapie HPT question.

So for the first time I bought some of the "first signal" tests....the one with the dropper. Well I tested tonight and after 3 min no second line. Let it sit and went back a few min later (before 10 min had passed) and there was a very very faint line. I tried to take a pic but my camera sucks and won't focus on it. So my question....is this brand notorious for evap lines? I have never had a test that got evap lines so I don't really know if that's what it is. I do plan on testing with FMU tomorrow.