Read observed-day metrics carefully
A visit date is not an exact biological event time.
Day zero is the start label
The start date is day 0. The next calendar date is day 1. Dates are treated as calendar labels, so a daylight-saving clock change does not make a calendar day shorter in the arithmetic. A single trial supports days 0 through 365.
Mean recorded observation day
The notebook multiplies each visit's newly observed count by its day number, adds those products and divides by the total recorded count. For four new seeds on day 3 and six on day 5, the mean recorded day is (4×3 + 6×5) ÷ 10 = 4.2.
This describes when you recorded the seeds. If you did not visit between days 3 and 5, some of those six may have met the rule earlier. The mean is not a continuous-time germination estimate, and it is undefined when no successes have been recorded.
The 50% observed day
This is the first recorded day on which the cumulative count reaches at least half the starting seeds. With 21 starting seeds, the threshold is 11. The app does not interpolate between visits. If fewer than 11 are ever recorded, the threshold is labelled “Not reached,” rather than inventing a date.
Read the chart as a record
The stepped chart joins cumulative recorded totals and marks visit points. A flat segment means no additional count has been recorded in that interval. It does not establish that nothing happened between visits. The observation table is the full accessible record behind the plot.