How my oldest son learned to write 1-10 in Chinese Charaters

Today I told my oldest son E who has just turned 4 last month to practice writing Chinese Characters 1-10 and I told him that if he can write them out without any help then I'll give him a dollar. I was thinking there was no way he can do that just yet, so I was pretty confident that this task will occupy him for a good hour also. I printed out the practice sheet from my previous post. Covered them with plastic protecting sheets and gave my son some dry erase markers. It didn't take him long before he told me that he was ready to take on the challenge. I didn't think he could do it but still pulled out a piece of paper and gave him a pen. I was really surprised to see that he actually wrote down all 10 characters and they even look decent. Here is a picture of him:

E and Chinese Character 1-10