Frozen test

I am using the clear blue advantage digital ovulation test (purple cap) This is my first time every using these.
I tested beginning on Monday, received just a circle (low fertility) tested Tuesday, low again. Wed, I received a solid smiley face. Of course i was thrilled! I tested the next day (Thursday) and received a solid smiley face again. I was a little worried that I was getting two of these in a row, so started researching a little. Tested friday, another solid smiley. I woke up this morning to test again and noticed that for the first time, the solid smiley had stayed. It never cleared like the previous times. 


In my research, i see where once you hit peak fertility the solid smiley stays for 48 hours. I'm confused because mine did not do that until the third day of received a solid smiley. Did i do something wrong, is that a common thing to happen? Please advise.