Clear blue advanced opk

[sil]

Has anyone used these? I usually use wondfo but I'm on vacation after having my Mirena out 12 days ago and was feeling very crampy so I bought this kit and it showed the flashing smiley with fmu and the solid smiley about 4 hours later. Attached is a photo of the inside lines. Do they mean anything? How accurate are these tests compared to wondfo? Has anyone had a false positive?

 

[sil]

Commenting to add I've never had a positive wondfo opk with fmu either. It is always mid morning or mid afternoon.