var config = {
    config: {
        mixins: {
            'mage/validation': {
                'Pritam_HideInfo/js/validation-mixin': true
            }
        }
    }
}

define([
    'jquery'
], function ($) {
    "use strict";
    return function () {
        $.validator.addMethod(
            'validate-minimumage',
            function(value, element) {
                 var xElemHtmlId = "Your Cofig field ID for X";// Plesae find id from View Source of the page
                 var xval =  $("#"+xElemHtmlId).val();
                 xval = parseInt(xval);
                 //console.log("x value="+xval);
                 //console.log("Y value="+value);
                 return (value >= xval ? false : true);
            },
            $.mage.__('Y must be less then number X')
        );
    }
});

<field id="myconfigx" translate="X" type="text" sortOrder="40" showInDefault="1" showInWebsite="0" showInStore="0">
                    <label>X</label>
                    <validate>validate-number</validate>
                </field>
                 <field id="myconfigy" translate="X" type="text" sortOrder="40" showInDefault="1" showInWebsite="0" showInStore="0">
                    <label>Y</label>
                    <validate>validate-number validate-minimumage</validate>
                </field>

sudo rm -rf var/generation/* sudo rm -rf var/di/* sudo rm -rf var/view_preprocessing/* sudo rm -rf var/view_preprocessed/* sudo rm
-rf var/pub/static/* sudo rm -rf var/cache/* sudo rm -rf var/generated sudo rm -rf var/composer_home sudo rm -rf var/page_cache sudo rm -rf var/view_preprocessed sudo rm -rf pub/static/frontend/* sudo rm -rf pub/static/adminhtml/*