Peak fertility result on first day of use (Day 8)

Using the digital OPK for the first time. I have fairly irregular cycles which are around 27-28 days long but based on body temp and crrvical mucus I think I ovulate around day 16 and have a short luteal phase. Anyway, to be safe I thought I would start with the OPK on day 8 so as plenty of time to establish a baseline in case I do ovulate earlier. First test came back peak fertility. I'm sure it's wrong as I know the point of testing before fertile days is to establish a baseline, and it can't have a baseline without having been used before. Not sure what to do now as it says not to test again after the peak fertility sign has been shown (but in this case, clearly wrong).