Unity - Scripting API:

public static function DoubleField(position: Rect, value: double, style: GUIStyle = EditorStyles.numberField): double;

public static function DoubleField(position: Rect, label: string, value: double, style: GUIStyle = EditorStyles.numberField): double;

public static function DoubleField(position: Rect, label: GUIContent, value: double, style: GUIStyle = EditorStyles.numberField): double;

Parameters

position	Rectangle on the screen to use for the double field.
label	Optional label to display in front of the double field.
value	The value to edit.
style	Optional GUIStyle.

double The value entered by the user.

Make a text field for entering doubles.