See function FileWrite , there is Note below there
Numbers will be converted into a text at output (see the Print() function). Data of the double type are output with the accuracy of 16 digits after the decimal point, and the data can be displayed either in traditional or in scientific format - depending on which format will be the most compact. The data of the float type are shown with 5 digits after the decimal point. To output real numbers with different precision or in a clearly specified format, use DoubleToString().
Numbers of the bool type are displayed as "true" or "false" strings. Numbers of the datetime type are displayed as "YYYY.MM.DD HH:MI:SS".