Fertility Friend uses a few different markers on your chart to give you more details on your data.
The open circles or clear dots on your chart mean that you have entered something in your data that may make those temperature points unreliable. In most cases it is the time the temperature was taken or that you entered that you were sleep deprived.
Your temperature was taken later than your usual time for this cycle and may cause inaccuracy.
Your temperature was taken earlier than your usual time for this cycle and may cause inaccuracy.
Please refer to the Chart Legend for full details on all the symbols and annotations displayed on your chart.