He seems to be saying that the market value of Twitter is $40B less than what it was before stuff happened. "Value destruction" tends to be applied to "stock" (like market cap) rather than "flow" (like revenues).
He's basically saying Twitter is worth $4B, given that he paid $44B and seems to be saying $40B of values was destroyed.
Losing $40B in less than a year is, uh, remarkable.