it depends on a lot of things... but that's quite a bit regardless
If you'd been cutting, your body will really be primed for growth...
If you are taking something that causes a good deal of water retention, it's fairly easy to gain 15 lbs of water quickly....
If you have increased your calories significantly, and quickly, you can gain a good deal quickl...
And if you put all those together, 22 lbs isn't impossible!
Heck, I gained 41 lbs in less than a week post contest, almost all water, but in the 6 weeks since then, I dropped 20 lbs, and now have packed at least 15 of that back on, up a total of 36 lbs or so in a little less than 7 weeks post contest.