How many DPO am I??

Lauren • Married August 2014, boy mom, first 💙 born July, 2016, #2 💙 born December, 2018.
So I used OPKs for the first time this cycle. I had a clear surge on the morning of 2/27, Friday. How do I know how many DPO I am? Deciding when to test and I know that I am around 10-12 days past ovulation, depending on what counts as day one. The difference in DPO makes such a big difference when testing early so I want to be sure.  Any guidance greatly appreciated!