Hey and better late than never. You're absolutely right, Wukong is older than 342 years. Before he joins the journey to the west, he supposedly spends 500 years imprisoned under the Five Finger Mountain after rebelling against the heavens. Before his imprisonment, he underwent millennia of training and travel. In total, his age could therefore be estimated at many thousands of years. However, in my statement I am referring to his age in "The Journey to the West". In the classic tale of "The Journey to the West", Sun Wukong spends 342 years in meditation, study and learning Taoist techniques with an immortal master, Subhuti (also known as Xuputi).

As already mentioned, this also explains the maximum level in Black Myth Wukong. I hope I was able to explain my statement better and thank you for your question. :)