Clear blue dating tests - how accurate?

Rebecca
Does anyone know how accurate they are? Mine came back at 1-2 weeks which means 3-4 weeks pregnant. The app tells me I'm 5+1 days based on my period so is the test behind or are my dates wrong? I have a spare test I will do in a couple of days so hopefully it should go to the next bracket but I'm a bit worried it's saying behind what I thought I was xx