very bad chart..
they are heavily under-estimating Y-20 production from 2024 onward. just like they did with J-20. WS-20 finalized, Xian is planning for full scale production.
Given what we've seen elsewhere in Naval and Air Force procurement, I'd expect a minimum of 24 per year for a Y-20 MRTT.
So 10 years time, there would be 240 tankers in total.
But my guess is that the modern Chinese Air Force combat fleet will grow to at least 2400 aircraft. That would imply a requirement for 600 tankers. Then you have at least another 100 airlifters required as well.