01
The sheet is summarized first
Posh does not send every row to the model. For each sheet it keeps the headers, the first 20 rows, and column stats for up to 200 rows. Numeric columns get a min, a max, a sum, and a mean.
02
Start from the file you already have
Drop a sales sheet, a survey, a pipeline, or a KPI workbook. If a number is not in the file, it should not appear as a fact on the report.
03
The report is asked to name the cell
Each fact is asked to say where it came from. For Excel, that place is the sheet and the cell. If the file does not contain a figure, the report should not add one.