When written literally, a number is either an integer, or zero or more decimal digits followed by a dot (.) followed by one or more decimal digits and optionally an exponent composed of "e" or "E" and an integer. It corresponds to the <number-token> production in the CSS Syntax Module [[CSS-SYNTAX-3]](https://drafts.csswg.org/css-... As with integers, the first character of a number may be immediately preceded by - or + to indicate the number’s sign.
5.00004e+06
就是 5.00004 x 10^6 = 5000040