Welcome to our NS Community, Rrey. It used to be just one package, but now you can choose. The basis of it is just the free travel on the weekends, and now you can add the 40% discount for during the week in the off peak hours.

The extra costs with Weekendvrij are only €3,10 a month. It is already profitable with an amount of more than € 7,75 for a normally priced ticket.

https://www.ns.nl/en/nsflex/webshop#/bestelling/producten/4/options

Thanks Laura. It was a bit confusing as with weekend vrij subscription, you can get 40% off for people who travel with you on of peak times, but not subscriber himself. Find it a bit strange - if my understanding is correct. 

It is correct, and the same strangeness also applies to those who have a Weekend Voordeel season ticket and have people travelling together with them during off-peak hours on weekdays.