2 different holders different results

I started testing on same day with 2 different holders with the same urine. One said peak fertility last night, the other said high fertility. This morning one still said high and not peak. I am testing for ivf transfer as advised by my clinic however the timing of LH surge is crucial to inform date of embryo transfer. How can i be sure of date if they are saying different days for the LH surge?! This has huge clinical implications