Not understanding the ovulation calendar

Brandy
I'm new to glow and have been tryin for a lil over 6 months. Not trying really hard by tracking and taking temps but now I'm worried so I signed up with glow. I'm tycoon my third and my first to happened way faster than 6 months but the ovulation calandra says that I'm ovulating for awhile and everything I read online says u really only have a 24 hr window so how do I no which day to try on. I would go by the ovulation tests but all the ones I find r really expensive for me to keep buying them and not be ovulating. Any help would be appreciated. Thank you