How much does everyone trust ovulation tests?

Hey,

So last month I used the clear blue digital advanced tests (I know there’s not supposed to be much different between cheapies or these but this is what I had in the house).

Peak showed up on cd15.

However today I started my period on cd28 this morning around 7am.

If what I’ve been told from a friend via doctors is right, ovulation is 14 days before the first day of your next period. This would mean my ovulation day was actually cd14. And if exactly 14 days would have been in the morning when the test predicted high.

Is ovulation that accurate? Or was the test probably right and the time from ovulation to period was just 13 days?

The reason I have trouble predicting is because my cycle can be different each month. And I’m doing a modified FET this cycle and want to know how much I can rely on the ovulation tests.