Improve string length function documentation to clarify pointer arithmetic usage

Author: chrisdedman

doc/AstraKernelManual.pdf

@@ -47,7 +47,8 @@ \subsection{\texttt{strlen(const char *str)}}
 \paragraph{Overview}
 This function counts the number of characters in a null-terminated string,
 excluding the null terminator itself. It returns the length of the string as an
-unsigned integer.
+unsigned integer. This function uses pointer arithmetic to traverse the string, 
+performing mathematical operations directly on the pointer values.
 
 \paragraph{Return Values}
 \begin{itemize}