I might be the only person who messes with this...but when I can't do exactly 12 hours, I up or lower the squirts depending on the discrepancy, at an attempt to keep even blood concentration. For example, if I know I'm going out real late that night and I won't be able to apply until 16 hours, I will give an extra squirt. OR, I will squirt extra when I come home, but the next morning, roughly 8 hours later, I will decrease a squirt.