4 chickens would theoretically eat 1 lbs a day between the four of them. So 22 kg = 22*2.2=50.4 lbs would last 48 days.
However, if you let them free range or give them a lot of scraps and treats they may not eat 1 lbs a day. On the other hand if your feed is going quicker than 50 or so days you may be feeding some other critters along with the chickens, such as mice, rats, etc.
I hope this was what you were asking about.