Remember though you can't compare betas with other people - it matters what your levels were to start with, if you started off with HCG of 0 (totally normal) and then it doubles over time, you end up with a much lower level on the same day as someone who started off with HCG of 5 (also totally normal)
Example: 0, 1, 2, 4, 6, 12, 24, 48 versus
5, 10, 20, 40, 80, 160, 320 and so on
Still both could be totally viable pregnancies