DMS: How to allocate 1024Mo of Memory for the DMS11GR2 running with Glassfish ?

Hi Experts,
On Glassfish console, i have these two lines:

-Xmx${JVM_HEAP_SIZE}
-Xms${JVM_HEAP_SIZE}

What is ${JVM_HEAP_SIZE} value ?

I then read domain.xml, and i see :
 <servers>
   <server name="server" config-ref="server-config">
     <system-property name="JVM_HEAP_SIZE" value="1024m"></system-property>
     <system-property name="JVM_HEAP_SIZE_XMN" value="512m"></system-property>
     <system-property name="JVM_PARALLEL_GC_THREADS" value="2"></system-property>
     <system-property name="MAX_THREAD_POOL_SIZE" value="12"></system-property>
     <application-ref ref="mobile" virtual-servers="server"></application-ref>
     <application-ref ref="__admingui" virtual-servers="__asadmin"></application-ref>
     <resource-ref ref="jdbc/__TimerPool"></resource-ref>
     <resource-ref ref="jdbc/__default"></resource-ref>
   </server>
 </servers>

and

 <config name="server-config">
     <system-property name="JVM_HEAP_SIZE" value="1024m"></system-property>