This notice was the first phase of approval. He did file the next phase as you said he received his conditional green card
The Notice you have is the approval for the visa petition that you filed on his behalf. Based on that approval his application for Adjustment of Status was approved, after which he received his conditional green card.
Samuel Ouya Maina, Esq. 415.391.6612 firstname.lastname@example.org Law Offices of S. Ouya Maina, PC 332 Pine Street, Suite 707 San Francisco, CA 94104
Hi! The above answers are correct. The letter that you have in your hands is merely one that was sent to you during the first phases of his petition. Good Luck!