I've never used a FRER, but I've had evaps come up immediately.

I can see the line, but it's borderline enough that I wouldn't trust it 100%. Test again in a couple of days, or better yet, have a blood test drawn. 7dpo looks promising as an implantation dip, and if it was, then 8dpo would have been too soon for the hcg to register. But, by 12dpo, you should have enough to test positive.