The number of placeholders for digits to the right of the symbol determines the number of digits in the exponent. If the exponent is negative, a minus sign is displayed directly before an exponent with E-, E+, e-, e+.
如果指数为负数，则在包含 E-、E+、e- 和 e+ 的指数前显示减号。如果指数为正数，则仅在包含 E+ 或 e+ 的指数前显示加号。