Question about ovulation testing!!

I took a test this morning, and it showed no LH surge.
I took one again at 5:00 and it was hard to tell, but I was leaning towards positive LH surge. 
I took one again at 9:00, just 4 hours later, and it was less dark than the one at 5:00. 
It was my understanding that the tests showed ovulation within 12-36 hours. Could mine have just showed that small window today?
I plan to take one again tomorrow, but I'm wondering if anyone else has any knowledge or experience with a similar situation. Thanks for any input!!
TTC#1  
10 months