Why is SAL reporting this loop as a potential buffer overrun?

Question

// Global:
const WCHAR g_Table[] = L"AbCdEfGhIjKlMnOpQrStUvWxYzaBcDeFgHiJkLmNoPqRsTuVwXyZ2468013579";


// In function:
void myFunction()
{
    WCHAR *rand