Document radial_center_offset bounds

doc/classes/TextureProgress.xml

@@ -33,6 +33,7 @@
 		</member>
 		<member name="radial_center_offset" type="Vector2" setter="set_radial_center_offset" getter="get_radial_center_offset" default="Vector2( 0, 0 )">
 			Offsets [member texture_progress] if [member fill_mode] is [constant FILL_CLOCKWISE] or [constant FILL_COUNTER_CLOCKWISE].
+			[b]Note:[/b] The effective radial center always stays within the [member texture_progress] bounds. If you need to move it outside the texture's bounds, modify the [member texture_progress] to contain additional empty space where needed.
 		</member>
 		<member name="radial_fill_degrees" type="float" setter="set_fill_degrees" getter="get_fill_degrees" default="360.0">
 			Upper limit for the fill of [member texture_progress] if [member fill_mode] is [constant FILL_CLOCKWISE] or [constant FILL_COUNTER_CLOCKWISE]. When the node's [code]value[/code] is equal to its [code]max_value[/code], the texture fills up to this angle.