Cheat Engine

[cheatengineuser14]

I want to start this post clarifing that my idea is test the program and start working in HEX edit.
I installed the Cheat Engine 6.3 program. I selected a Facebook Game (FLASH). I opened the game, and the Cheat Engine. In the Cheat Engine selected the second process of Flash (using Firefox). With the value type in 4 bytes, the scan type in “exact value” I put the quantity of one of the resources of the game (wood): 505. Then New Scan, First Scan. 70 results appeared.
Then I used that resource (50 of the 505 of wood). From the list one was updated (the value) to 455. I clicked on this line and changed the value to 800. I returned to the game, but the value continued in 455.

Now the question: Anyone knows why didn’t work? I insist. My idea is test the Cheat Engine and acquire knowledge.

I will appreciate any kind of help or suggestion.