At this point, this is unfortunately not possible, and is just a little helper text for the admin
One workaround would be to use jquery. Open up wrapper.html and find this
	
	
on a new line below we will target the field container and insert some text
	
	
	
		Code:
	
	
		$('#acf_myfield_container').append('<p class="help-block">my text here</p>');
	 
 adjust acf_myfield to match  your field name and adjust the text