I got a 2-3 with this one at 4 weeks / 14 dpo (according to my charting dates). I got my shadow of a bfp at 8 dpo and the weeks estimators were negative until 10 dpo when I got 1-2. I got a 3+ at 5 weeks / 21 dpo.
I think for me it was early implantation.
With DS I didn't even test until 18 dpo (I only tested because I was late - DS was a surprise), but I got 2-3. I don't know when the earliest I would've had 2-3 with him, but I know I didn't get my 3+ with him until a bit later than I did with this one.
Also, remember with these than concentration in urine can make a difference in the result. I was worrying about mc with DS. I had already had a 3+ at that point and because I was worried, I took another weeks estimator to make sure it hadn't changed, and it had gone down to 2-3. So that was a concentration issue.
Another member had compiled hcg values associated with weeks estimator:
https://babyandbump.momtastic.com/pregnancy-tests/2418547-3chords-collection-beta-hpt-facts.html
So really when implantation occurred can make a difference, along with concentration. While there's a standard doubling time for hcg, sometimes hcg rises a little slower or a little faster depending on the pregnancy.
I know it's so hard not to worry, but please try not to let the weeks estimator worry you too much as there are a lot of things that can impact the results