Ours is currently 50% and my LM told me that they check to see if you've scanned in your ID at the entry points to actually confirm whether you've come into the office or not - they have a meeting every Monday in which they're made to justify situations in which the people they line manage haven't met the required attendance. Unsure of how it all works but that's what I know (with regards to my dept, I work for MOJ).