How much more tranny fluid do YOU think it need? How do you come up with that amount?
If you followed proper procedure then you had enough fluid in there. You worry about not putting enough in, but you shoud worry about putting too much in also.
Why dont you lift and level the car, remove fill plug, run it through the gear, make sure the fluid is within 30C-55C, then pump in some fluid. If it drips back out after you remove the pump tube, wait at least 60 seconds (per DISv44) before replacing the fill plug. Then you should be done.

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00 E39 DINAN S1 //M5 (82k miles)
06 E53 DINAN 4.8iS, born 2/18/2006 (126k miles) http://www.xoutpost.com/bmw-sav-foru...s-my-dslr.html
90 Straman Z32 TwinTurbo Convertible, (1 of 44 ever made) 5 speed, 444rwhp/451rwtq
01 360 Novitec Spider F1 (26k miles)