Pregnancy test

What does it mean when a test does this? Does every test do this when it’s dry? Or does it indicate that there was hcg present has this happened to any of u and you been in fact pregnant or it happens with every test? Thanks I’m ttc I had unprotected sex 6 days ago so I’m hoping I get a positive I have irregular periods but I have 2 sets of twins lol so I know I can get pregnant anyways comment thank you 😊