Maybe I'm misunderstanding the calculator on MrMalty? According to yeast viability determines the number of smackpacks or vials needed for the required size for the starter?Rule of thumb.
If you make 2000ml starter at 1040 and pitched one vial into it, you will get about 2 vials of yeast.
If you need 4 vials (lagers) make 4000 ml starter and pitch one vial into it.
This goes for average beer (1050 or so) and 5 gal of wort.
If you have higher gravity beer or more wort you need more yeast.