Sounds hopeful to me hon. I had those "squint and you might see something" on First response for four days after AF was due and then all of a sudden it went REALLY dark on the 5th day. I had spotting on the day AF was due with this pregnancy so I thought I wasn't UTD and had 3 glasses of wine (oops!!)
I had very low HCG levels to begin with, the doc thought it was a non viable pregnancy but here I am, 12 weeks and still UTD!! I found using the digital ones that say "pregnant" or "not pregnant" helped ease my mind a little cause it was a def answer rather than trying to guess at a faint line.
And I believe if the line turns up in the time then it's not an evap line
Good luck hon!!