Missed morning urine for ovulation test

Hi, please can you tell me if my CD 15 positive can be relied on or not?

This is my second month of tracking using the same reader. On CD 12 I used it correctly (first morning urine) and on CD 13-14 I forgot so tested with urine in the late morning (drank one coffee in between).

CD 12 - negative - tested with first urine

CD 13 - negative - tested with later urine

CD 14 - negative - tested with later urine 

CD 15 - positive (flashing smiley) - tested with first urine

Can I rely on the positive result on CD 15 or is this invalidated by the previous two days?

In future, if I forget to test first thing, should I skip a day or test in the late morning?

Thanks