For loops in MB Blocks with MB Builder

I want to create a for loop to render a clonable text field in order to create LIs.

<ul id="pros-list">
   {% for i in pros %}
      <li>{{i}}</li>
   {% endfor %}
</ul>

That's based on the example in Twig, but I realize that it won't get the array in my custom field called "pros" because it isn't between brackets, the issue is that if I add {{pros}} inside any kind of {% %} it crashes WP.

Also, I want to do a math equation with the fields, something like ({{a}} + {{b}})/2, how can I achieve that?

Thanks in advance!

Cheers.