2 Antminer U2's will never mine 1 btc in 7 months. More like 400 months.
If you start now, you will never get 0.02 BTC with 4 GH/s (2 * U2).
But, Chrithu could have been hashing for months already since the difficulty was much lower.
You can use a profit calculator to check your expected mining revenue and profits.