Ovulation

I’m new at this whole TTC thing. I haven’t started doing temps or anything yet but I was wondering if I should go by CM or glow’s prediction for ovulation until I start doing temps and tests. I’m just wondering because glow said a certain type of CM happens when you’re most fertile which is off by about 2 days from glow’s prediction. Which one should I go with for this cycle? Did I ovulate sooner than expected maybe? Thanks!!