The sig command returns x expressed as a floating-point number rounded to n significant digits.

$\mathrm{MapleTA}:-\mathrm{Builtin}:-\mathrm{sig}\left(3\,20.8571\right)$

$20.9$

The MapleTA[Builtin][sig] command was introduced in Maple 18.

For more information on Maple 18 changes, see Updates in Maple 18.