s: the string
num_bytes: the maximum number of bytes to return (defaults to 1)
The semantics of this function is subject to change as various applications implement it. If the string is in a right-to-left script, the returned first characters are from the right of the string.
While this function is syntactically Excel compatible, the differences in the underlying text encoding will usually yield different results.
While this function is OpenFormula compatible, most of its behavior is, at this time, implementation specific.