Ovulation test help

These are the clear blue smile face tests.

I think I ovulated on Oct 17

Beginning of last period was Oct 3

I usually have a 28 day cycle, but before this had a cycle of 30 days (highly unusual for me, last time I was that late was in 2016.. I think it related to the prenatal vitamins I had begun taking)

Anyways, besides the point. Just wondering if anyone here looks at the lines of the tests, even though they just tell you to look at the digital part?

I got a smile on oct 17 evening and nothing on oct 18 mid morning

Wondering if it was a false positive?