Two field multiple values
Sounds like the field collection module would fit your needs perfectly, however that doesn't have a Drupal 8 version yet so it's hard to know what the Drupal 8 site is using to do this.

For Drupal 8 there is a sandbox version of the field collection module however I'm not sure how stable it is.

Another possibility is that they have created a custom field for their site that is a combination of multiple elements.

If you want any sort of compatibility with the two sites' data the I would suggest asking them how they have implemented theirs and use that option for your Drupal 7 site.