What day would I have ovulated according to OPKs?

My OPKs say that my peak 1.07 was on CD 17, on CD 18 at almost 1am it was at 0.86, on CD18 at 3pm it was at 0.72 and now today on CD 19 it says low 0.31. If the peak was my surge, what day would I have ovulated?