Totally confused..Please help...🙈

Hey ladies does any one else have this problem..I've tried a few ovulation calulators and each one says different things...and most don't match with glow...most say I should have been ovulating before the time glow states..so hhhmnm..???? what now it's all getting a little confusing as glow states I am 6DPO but going by all the other calulators I will be 10-12DPO...!! Just wondering if anyone else is as confused as me..I thought u count 14days from the first day of your last period?? Or am I totally going wrong..any advise/help would be great thanks xGx