Congratulations!!!
I wouldn't worry about the Clearblue predictor thing. It measures HCG levels and there is a great variation on what someone's HCG level is at particular points in pregnancy. When I was pregnant with my son, I had three HCG level tests during the first few weeks. One actually was slightly off the top end of the charts. So you can be accurate in your ovulation prediction date and still read slightly out on the Clearblue predictor, as it will go on around about average HCG levels. Sorry, I hope my ramblings makes sense.