Ovulation question

I've been taking opk tests for 4 days now. Last AF came on the 6 and my cycles are usually 30-33 days apart. Right now, I'm on CD 20. According to Glow, I should start ovulating on the 25th. The tests are coming back like this 
Does the line get darker as ovulation draws closer? 

Glow Resources

Let’s Glow

Glow is here for you on your path to pregnancy

Glow helps you navigate your fertility journey with smart tools, personalized insights, and guidance from medical experts who understand what matters most.

25+ million

Users

4.8 stars

200k+ app ratings

20+

Medical advisors