Q for any Oko plus users.... Does the 10 litre bag fill a litter tray? I'm a crumb user and still frustrated by the tracking, I tried Classy Cat from Zooplus but wasn't overly impressed so was thinking of trying Oko plus. Chick crumb is so economical I know that 'normal' litters will always cost more but was wondering whether a bag was enough to fill a tray, if it is then that's not too bad costwise.