Clearblue Advanced OPK Question

So I purchased the clearblue advanced digital OPKs, yesterday was my first day using it CD8 (and it was Empty O) which I expected. Today when I used it, it was a Flashing Smiley (CD9) which totally took me off guard because when I would use my cheapie OPKs my LH surge is typically around CD17/18. Is this digital test just suggesting there’s a surge in my estrogen now? Is it faulty? The lines were progressed from yesterday’s test so I’m confused. Thanks!