Good question, well presented etc etc...
You'd expect higher attendance from higher ranks and, personally, I reckon 50 for an officer is about right (perhaps fewer from a subaltern and more from an OC?). How that ties in with the forthcoming 32 day year I'm not quite sure.... it certainly makes a mid-year review laughable - even if you spread your days you've only done the civvy equivalent of three working weeks between appraisals!!
Is there no definitive answer written down as to how many days makes a regular attender or is it just down to the crayon wielding subbie writing your CR?