How to set Caldera Forms field default value from ACF field. See: https://calderaforms.com/doc/caldera_forms_render_get_field/

caldera-forms-field-default-acf-field.php

<?php
/**
* Set Caldera Forms Field default from ACF field
*/
add_filter( 'caldera_forms_render_get_field', function( $field )  {
  //Change your field ID here
  if( 'fld123456' == $field[ 'ID' ] ){
		  $field[ 'config' ][ 'default' ] = get_field( 'field_name' );
  }
  return $field;
});