auto(integer) the number of automatically formatted decimals, the default is auto(3), i.e. three significant digits not counting the ones (i.e. the digit to the left of the decimal point).  This means 1.234 and 0.123 might be displayed, while 12.345 or 0.1234 will be trimmed. A probable integer is reported without decimals. A very large or small number will be displayed in exponential format. Specify dec( ) or bdec( ) to disable it.
来源于 help outreg2

上面的意思是把12.345储存为1.234？感觉不是这样的啊，仅仅是保留位数的问题，本身大小不会变动啊。
还是说这是两个分开的例子，所以想请教大佬们这个auto具体指如何保留小数位