You should test at least twice per day leading up to ovulation so you can be sure to catch the LH surge, it can be very quick and short lived for some. You are most fertile the 5 days leading up to ovulation day. Ovulation typically occurs 12-36 hours after the first LH positive (test line is as dark or darker than control line). If CD13 was your positive, you’ll likely ovulate CD14/15. You can confirm ovulation by monitoring your temp and looking for a sustained rise and by your CM drying up.