The 'change ticket conditions' only allowed you to select from a specific set of options, I would often use it to book AF PE, or book one way in Y and one way in J, since that was the only way to do it via the KLM website, but it didn't allow you to select the booking class.
For some flights (e.g. AMS-TLV), it would only have the option to change one of the legs to J, for some others it might have 2 or 3 options.

But now KLM have changed their website and you get the ticket conditions when you are still in the flight selection screen, and you cannot longer see/change the ticket conditions later on as before.