Why description catch twiter description instead meta description?

[SalahAdDin]

I'm using this package for fill a collection with title and description from url, the code is this:

"submit .js-save-website-form": function (event) {
        var title, description;

        // here is an example of how to get the url out of the form:
        var url = event.target.url.value;

        console.log("The url they entered is: " + url);

        extractMeta(url, function (err, res) {
            console.log(res);
            console.log(res.title);
            console.log(res.description);

            if (event.target.title.value) {
                title = event.target.title.value;
            } else {
                title = res.title;
            }

            if (event.target.description.value) {
                description = event.target.description.value;
            } else {
                // decoding HTML special characters in res.description
                // creating a text area with red.description as the HTML.
                // them putting textarea.value in desc
                console.log('res.description: ', res.description);
                var textArea = document.createElement('textarea');
                textArea.innerHTML = res.description;
                description = textArea.value;
                console.log('Description: ', description);
            }

            // var cleanKeywords = cleanString(title, desc);
            // var keywords = createKeywords(cleanKeywords);

            // If user logged in, insert website
            //  put your website saving code in here!
            if (Meteor.user()) {
                Websites.insert({
                    title: title,
                    url: url,
                    description: description,
                    votesUp: 0,
                    votesDown: 0,
                    createdOn: new Date(),
                    createdBy: Meteor.user()._id
                });
            }
        });

        $('#website_form').modal('hide');
        return false;// stop the form submit from reloading the page

    }

When i fill this form i have a surprise: this take the twitter description instead meta description. You can see there a comparative images:

I don't understand why happen this, can you help me?