Confused about DPO...help lol

Arlethia • Mommy of 5, engaged 💍, #6 &#7 🤰🏾March 2020

Ok so I use 2 different ovulation calendars...Glow says ovulation was on 4/23(8 DPO) but the other one says 4/18(13 DPO). AF not due until 5/3 but got BFN yesterday with a cheapie. I'm new to keeping up with ovulation and I'm not really sure which one to go by. Am I calculating it wrong?