Clear blue digital opk surge predictor wrong

So I used the clear blue digital test this cycle and got blank smiley the first 3 days then a soils smiley on the 4th day. This didn't seem right to be because I was only on cd 9 or 10...I have very regular cycles and tend to ovulate around cd 13 or 14. So I used the first response non digital one and the line wasn't even close to the same colour as the control line. I kept testing with the first response and just got the surge today ( cd 13). Has anyone else had this issue with the digital tests? - http://glowing.com/community/topic/475264?utm_source=android&utm_medium=shared_to_third_party&utm_campaign=glow_community