Update note

Author: kgryte

lib/node_modules/@stdlib/stats/incr/mmean/README.md

@@ -77,7 +77,7 @@ mu = accumulator();
 
 ## Notes
 
--   Input values are **not** type checked. If provided `NaN` or a value which, when used in computations, results in `NaN`, the accumulated value is `NaN` for **all** future invocations. If non-numeric inputs are possible, you are advised to type check and handle accordingly **before** passing the value to the accumulator function.
+-   Input values are **not** type checked. If provided `NaN` or a value which, when used in computations, results in `NaN`, the accumulated value is `NaN` for **at least** `W-1` future invocations. If non-numeric inputs are possible, you are advised to type check and handle accordingly **before** passing the value to the accumulator function.
 -   The first `W-1` returned mean values will have less statistical support than subsequent mean values, as `W` values are needed to fill the window buffer. Until the window is full, the returned mean equals the [arithmetic mean][arithmetic-mean] of all provided values.
 
 </section>