koken lens variables issue

gistfile1.txt

<p>Work
  <koken:load> 
    {{ _parent.album.context.position }}
      / 
    {{ album.counts.total }} <!-- prints the number of albums in this set --> 
  </koken:load>
</p>

Hello,
I'm dealing again with lens variables and having some problems.

This time i'm in the page within a Set, where 10 albums are displayed. I wanted to get for each album its numerical position in the list of all the albums of the set, and display this information like 1/10 for the first album, 2/10 for the second, and so on....

So I took {{ album.context.total }} and {{ album.context.position }} and played a little while with them (i tried lot of things cuz i could not understand how to implement them from the documentation), but no result...
I'm making a custom theme, and this time i'm working on album_index_loop.html. How do the lens variables work?

i was able at least to make the {{ album.context.total }} work. Nonetheless {{ album.context.position }} does not print anything