How do you know if it's an indent?

When I first got pregnant I didn't know what to look for or really want I was doing...now for my second child I feel a little more knowledgeable, but the one thing still confusing me are pregnancy test? I felt I saw a line this morning if I ovulated when my app says I did, I would be 10dpo...

But my question is...if I'm really 10 dpo...would it definitely show up on a FR test...or possibly not? When I first got pregnant a little over 2 years ago I randomly took a test, an the line was there...i went to the doc an was 4weeks an a few days...so I didn't struggle with reading test...so can someone NICELY not rudely explain what the possibilities are here? I would greatly appreciate it