Problem at spanish version?

I want to show in related posts only posts since one month ago. I looked for it in Help and I found this:

How can I limit related posts to a certain time frame? For instance, I don’t want to show posts from two years ago.

Yes. In WordPress, go to “Settings” and “Related Posts (YARPP)” and make sure “The Pool” is checked in the “Screen Options” section at the top of the page. In “The Pool” section, check the box next to “Show only posts from the past X months.”

The problem is that in Spanish version, I can not enter a number X. I can see this text with a checkbox: “Mostrar únicamente Publicaciones de las pasadas UNIDADES de NÚMEROS”, but there is not space to write anything.

Thanks

https://wordpress.org/plugins/yet-another-related-posts-plugin/