#MISSING in a cell indicates that the cell contains no data, whereas zero in a cell is a data value. #MISSING decreases the database size and improves performance.
You can replace #MISSING by selecting the cell and entering a value. You can also replace irrelevant data in a cell and save the cell as #MISSING, which writes #MISSING to the database.
You can select contiguous cells by clicking in the upper-left cell in the range, and then pressing Shift+Click to select the lower-right cell in the range. You can select rows and columns by clicking row and column headings. Select a range of rows or columns by using Shift+Click.
If the designer sets a form to suppress missing data, and an entire row contains #MISSING (no data), that row does not display on the form.
You can also enter #MISSING using Smart Lists. See Entering Data with Smart Lists.
The cells are set to #MISSING when you save the form.