In the help document of str() function, following information is given

" If nExpression is of numeric or float type, STR( ) returns a value using scientific notation if nLength is less than the number of digits in nExpression. If nExpression is an integer, STR( ) returns a string of asterisks, indicating numeric overflow, if nLength is less than the number of digits in nExpression. "

"If nLength isn't included, the length of the character string defaults to 10 characters."

Ali Altun