Play Framework 2.3 jvm memory on run

I'm trying to increase Jvm memory of my application but doesn't matter what I use I get 256Mb as max memory. To see the max memory I am using

val instance = Runtime.getRuntime();
val  mb = 1024 * 1024;
val maxm = ("Max Memory: " + instance.maxMemory() / mb);

I tried to to run the app with...

activator -Xms512M -Xmx512M run
activator -mem 512 -J-server run //this doesn't run
env JAVA_OPTS="-Xms512m -Xmx512m"  &&  activator run 
env JAVA_OPTS="-mem 512" &&  activator run 
env JAVA_OPTS="-XX:MetaspaceSize=64M -XX:MaxMetaspaceSize=512M"  &&  activator run 
env JAVA_OPTS="-DX:MetaspaceSize=64m -DX:MaxMetaspaceSize=512m"  &&  activator run 

Am I doing this on the wrong way?