Good luck everhopeful I have everything crossable crossed for you
As far as I'm aware it's just that the Clearblue HPTs have a much higher threshold for the level of hCG they detect. And that as levels for different stages of pregnancy vary so much from individual to individual, someone could be 6 weeks pregnant but with lower hCG levels than someone who's 4 weeks pregnant, but the CB digi would say they were both 2-3 weeks pregnant. So many women have panicked themselves with the dates that I personally wouldn't want to shit myself up unnecessarily
I did use the Clearblue fertility monitor (basically the same as their dual hormone OPKs) - complete waste of money for me, as I never got a high reading as I never produced enough oestrogen for it to detect rising levels to give me a 'High', so mine always jumped straight from Low to Peak. Which told me the same as the cheapie OPKs, as both were just detecting my surge - the CB was supposed to give me my whole fertile window
However it was a useful diagnostic in and of itself, as the lack of rising oestrogen and my total lack of any CM, plus scanty periods, meant we checked how my lining was doing in a natural cycle, and identified that it was too thin to have ever been able to support a pregnancy, and meant that we agreed that we would do monitored cycles with oestrogen support in between IVF cycles (we assumed that the cycle would fail and I'd have to wait 3 months before I could cycle again. We didn't expect it to work, me miscarry, but have 4 frosties on ice)
The monitor automatically cuts out as soon as you get your first Peak - it gives you a second Peak day by default and then switches straight to low, without asking for more piss sticks, as it assumes by the time it's detected a surge, ovulation is imminent
This is why it doesn't necessarily work if you have PCOS where LH levels can be higher and you can have multiple surges but no ovulation