Would guess that for some reason, they are only making available a Premium Room Reward for the Saturday night, whilst they are making Standard Room Rewards for the 2 nights. Don't know why they might do that, but perhaps they think they can let the Standard room itself for 2 nights of the weekend, easier than a Premium room. Thought that hotels had to make Standard rooms available for Awards if they have them available.
If we're talking about 12 May, if you want to stay two nights they are selling the King Superior Room for €274/night, but if you only want to stay one night they will only sell you the King Deluxe Room at €309.
It looks like the redemption availability reflects this.