pewc_number_field_step.php

<?php
/**
 * Return a step value of 100 for a specific field ID
 * Update the field ID in line 8 below
 * Update the step value in line 9 if you wish
 */
function demo_number_field_step( $step, $item ) {
	if( $item['field_id'] == 12345 ) {
		return 100;
	}
	return $step;
}
add_filter( 'pewc_number_field_step', 'demo_number_field_step', 10, 2 );