You didn't mention which model you have, but generally it is recommended that when filling up tranny fluid, you start out with 4 quarts. Start the engine and put the gear selector in each gear for a moment or two. Return the selctor to park and check the level, add accordingly. Most trannys take 6+ quarts. Check your owner's manual for specifics.

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member