记不太清了，好像是说数值型变量如果包含point话，就不需要设置长度，直接按原数据长度。

Numeric values in SAS for UNIX are represented as IEEE double-precision floating-point numbers. The decimal precision of a full 8-byte number is effectively 15 decimal digits.
这里8位是指二进制表示的长度，不是字符串长度

When a format is not specified for writing a numeric value, SAS uses the BESTw. format as the default format. 这里默认长度是12，所以90800000.87可以全部显示