This has probably been asked before...I have just started the Persona (now month 2) and this month, the persona came up with 2 days ovulation (on day 9 and 10). At the same time, this month I decided to try the digital ovulation tester (as I was told it could take at least 3 months to find out when you ovulate with the persona) and from day 8 until day 15, I have a smiley face (which means due to ovulate..?). I thought it would only have a smiley face for a couple of days... why has it done it for the whole 7 days? I assume Persona is more accurate?