Reading PT after 10 min.

So I took a PT late last night, and my husband said it looks like a vvvvvvvfl, but then took another one this morning and it’s a BFN.

Went back to see the one from last night, and I can see two blue lines. But they were not there last night.

Is that why we’re not supposed to read test after 10 min, because of false positives?

Thank you. 😞💔💔💔