How far along am I?

Hi- just wondering how others are calculating how far along they are? Some app says I am further along than others. Do you just count from the first day of your last period? In that case...does your cycle length not taken into consideration? Can someone count mine? My last period was 16 jan (first day) lasted 4 days. I'm roughly 32 days cycle but I only got a positive opk on 5/6 feb! Thanks in advance x