That's not what happened. You gave them 20,000 shares and in return you end up with 1 share, Its called a reverse split.
On a forward split you would get 20,000 for your 1 share.
Also understand that on a reverse split when you surrender the 20,000 the value of your remaining 1 share goes up 20,000 times.
Example: 20,000 shares worth 1 cent or $.01 = $200.00 after the reverse split at that instant the 1 share is worth $200.00. What usually happens though is that $200.00 value is short lived and proceeds to drop. Now that usual but not always.
However there are many reasons for both a forward split and a reverse split, and each situation is different depending on the needs of the company doing the split.