Hello, to resolve this issue I override the confirm method from de NumberPopup, then I send a 'Delete' input, this clear the buffer of the Popup. Here is the solution:

odoo.define('pos_custom.NumberPopup', function (require) {
    'use strict';

    const NumberPopup = require('point_of_sale.NumberPopup');
    const Registries = require('point_of_sale.Registries');

    const PosNumberPopup = (NumberPopup) =>
        class extends NumberPopup {
            constructor() {
                super(...arguments);
            }

            confirm(event) {
                super.confirm(event);
                this.sendInput('Delete');
            }
        }

    Registries.Component.extend(NumberPopup, PosNumberPopup);
    return PosNumberPopup;

});