docs: clarify role of N and in-place behavior in cumax

Author: YOGigx

lib/node_modules/@stdlib/stats/base/cumax/README.md

@@ -121,6 +121,8 @@ cumax.ndarray( 4, x, 2, 1, y, -1, y.length-1 );
 ## Notes
 
 -   If `N <= 0`, both functions return `y` unchanged.
+-   The first argument, `N`, determines how many elements are read from the input array `x` and how many results are written to the output array `y`. The function processes exactly `N` elements from `x`, advancing through the array using the specified input stride. Results are written in-place to the provided output array `y` using its stride. If `y` is larger than `N`, only the first `N` output positions are modified; all remaining elements in `y` remain unchanged.
+
 -   Depending on the environment, the typed versions ([`dcumax`][@stdlib/stats/strided/dcumax], [`scumax`][@stdlib/stats/strided/scumax], etc.) are likely to be significantly more performant.
 -   Both functions support array-like objects having getter and setter accessors for array element access (e.g., [`@stdlib/array/base/accessor`][@stdlib/array/base/accessor]).