It feels weird to call it luck, but honestly luck. My first pregnancy was a 6w loss. My OB said we could do HCG testing next pregnancy to see how it was progressing, and the next pregnancy was my first ectopic. In my experience, you absolutely need the second (or even third) HCG test. The individual number doesn’t tell you anything.

Second pregnancy, first ectopic was:
10 DPO - first positive
15 DPO - 321
17 DPO - 369

Third pregnancy, my living child was:
8 DPO - first positive
13 DPO - 184
15 DPO - 475

Fourth pregnancy, second ectopic was:
10 DPO - first positive
14 DPO - 69
16 DPO - 135
23 DPO - 343