How Do I Add More RAM To My Server?

I have a new Minecraft server. It currently only has 1024MB of RAM. I have 16GB RAM on my computer, so I really want to add more to my server. But when I add it, once I open it I get this error message:

"Could not reserve enough space for object heap"

The code I use for the batch file is:

java -Xmx1024M -Xms1024M -jar craftbukkit.jar
PAUSE

Is there something wrong with the batch file? I really need help with this because my server is very weak atm.

 

Code:

java -Xms1024M -Xmx1024M -jar craftbukkit.jar -o true
PAUSE

this is the lign in the wiki
http://wiki.bukkit.org/Setting_up_a_server

 

To use all 16GB, type 16384M instead of 1024M

 

What would I put if I only want to use 2?

 

java -Xmx2048M -Xms2048M -jar craftbukkit.jar