Kode dari tutorial https://solusipress.com/menambahkan-number-spinner-pada-forminator/

functions-2.php

<?php
add_action( 'wp_enqueue_scripts', 'solusipress_jquery_number' );
function solusipress_jquery_number() {
	if( is_page( 'forminator-test' ) ) {
		wp_enqueue_script( 'jquery-number', 'https://businessprofile.solusipress.com/wp-content/uploads/custom-css-js/18.js' );
		/* load javascript dari Code JS yang sudah dibuat */
		wp_enqueue_script( 'input-spinner', 'https://businessprofile.solusipress.com/wp-content/uploads/custom-css-js/105.js' );
	}
}
add_action( 'wp_footer', 'solusipress_forminator_format_number' );
function solusipress_forminator_format_number() {
	if( is_page( 'forminator-test' ) ) { ?>
<script type="text/javascript">										
( function($){
    
	/* ubah field number menjadi spinner */
	wrap_spinner( 'forminator-field-number-1' );

	$( '#calculation-1-field' ).hide();
	$( '#calculation-1-field' ).parent().append( '<div id="total_html" style="font-weight:600;font-size:22px"></div>' );
	set_total();
	$( '#calculation-1-field' ).on( 'change', function(){
	    set_total();
	} );		
	
    /* Kode untuk membungkus input number menjadi spinner */
	function wrap_spinner( id ) {
		$( '#'+id ).css( 'display','inline-block' )
				   .css( 'margin-top', '0px' )
				   .css( 'border', '1px solid #ccc' );
		$( '#'+id ).attr( 'step', '1' )
				   .attr( 'readonly', 'readonly' );		
		$( '#'+id ).addClass( 'input-text qty text' );
		$( '#'+id ).wrap( '<div class="quantity buttons_added"></div>' );		
		$( '#'+id ).parent().prepend( '<input type="button" value="-" class="minus">' );
		$( '#'+id ).parent().append( '<input type="button" value="+" class="plus">' );
	}
	
    function set_total() {
        var tot = $('#calculation-1-field').val();
        $( '#total_html' ).html( 'Rp' + $.number( tot, 0, ',', '.' ) );
    }	
	
} )( jQuery );	
</script><?php
	}
}