Explanation
This is a tricky use of N() that allows you to use it as a way to leave in-cell comments. It only works for formulas that return numeric results.
The N function takes a value and returns a number. When given a text value, the N function returns zero.
In this case, the primary formula the SUM function, and the N function simply evaluates the comment text and returns zero:
=SUM(F5:F8)+N("Q4 numbers are estimates")
=SUM(F5:F8) + 0
=410,750
The comment is visible in the formula bar when the cell is selected.
Related functions
N Function
The Excel N function returns a number when given a value. The N function can be used to convert TRUE and FALSE to 1 and 0 respectively. When given a text value, the N function returns zero.
