<itunes:duration> wrong on RSS feed created by Jekyll

I have a Jekyll site that I have a podcast feed that I created.

---
---
<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
    <channel>
        <atom:link href="http://mikewills.me/rss-podcast.xml" rel="self" type="application/rss+xml" />
        <title>{{ site.name }}</title>
        <description>{{ site.description }}</description>
        <link>{{ site.url }}</link>
        {% for post in site.categories.podcast limit:15 %}
            <item>
                <title>{{ post.title }}</title>
                <description>
                    <![CDATA[
                    {{ post.content | xml_escape }}
                    ]]>
                </description>
                <pubDate>{{ post.date | date: "%a, %d %b %Y %H:%M:%S %z" }}</pubDate>
                <link>{{ site.url }}{{ post.url }}</link>
                <guid isPermaLink="true">{{ site.url }}{{ post.url }}</guid>
                {% if post.podcasturl %}<enclosure url="{{ post.podcasturl }}" length="{{ post.podcastsize }}" type="{{ post.podcasttype }}" />{% endif %}
            </item>
        {% endfor %}
    </channel>
</rss>

Everything else works except for the <itunes:duration> tag. When I enter in podcastlength: 2:07 it outputs as <itunes:duration>127.0</itunes:duration>. Based on what I have researched, this is how everyone else is outputting the length. For some reason Jekyll seems to be breaking that down to seconds instead of 2 minutes and 7 seconds. What might I be doing wrong here?

If you are interested, full RSS source is here and an example post is here.

What @Julien Genestoux suggested worked.

"What if you put commas around "2.07" to force Jekyll to think of it as a string and hence not convert it? – Julien Genestoux Jul 30 at 13:31"