Error: Could not create the Java Virtual Machine

ok so i was trying to add more RAM to my tekkit server by adding a launch.bat file but whenever i run it i get:

Invalid initial heap size: -Xms8G
The specified size exceeds the maximum representable size.
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

i recently built my computer and i have 12GB of RAM so thats not the problem.
i have just updated java thinking that might be the problem.
i deleted any old versions of java.
does anyone have some suggestions? i would really apreciate any help.