Agree, “Review” is not an appropriate way of raising a support issue. If there is an issue it should be reported on https://github.com/hyyan/woo-poly-integration/issues
NumberFormatter is part of intl extension bundled with PHP since PHP 5.3 (2009): https://php.net/manual/en/class.numberformatter.php
If you are using a version older than that you should definitely upgrade. Please note that everything prior to PHP 5.6 is currently considered old and unsupported by the developers of PHP. There are no security releases for older versions.
And if you are running a multi-language site it makes sense to have the internationalization extension enabled..
This feature can also be turned off from the Settings page, ie: /wp-admin/options-general.php?page=hyyan-wpi under Features, Use locale number formats