Your function would only update one Gravity Form field with the one ACF field.
Looking at the GF Docs, you can see:
add_filter( 'gform_field_value_your_parameter', 'my_custom_population_function' );
function my_custom_population_function( $value ) {
return 'boom!';
}
This snippet would populate any field with the parameter your_parameter with the result of the function my_custom_population_function. In this example, that function returns the string boom!.
So I think you would need to repeat this for each field you wish to populate.
