i think when CVC are talked about as paying 1.6 bn they are referring to the enterprise value inclusive of debt.
If the value of 50% is 800m and there is 900m of debt in Steller. The CVC reduce the amount they pay be half of 900m if they assume the debt.
800m = Cash 350 to MFS and CVC get 50% of stella and 50% of the Stella debt of $900m, $450.