I think what you're seeing there does not really represent the physical memory usage of the app, but includes all shared and virtual reserved memory too. The real physical usage is probably something around 130MB.
If you have access to the server with an SSH tool like Putty:
1. install htop (sudo apt-get install htop)
2. run jcmd to find the PID of your app (e.g. in my case 2772)
3. run htop, find your PID and look at the RES column (what you see in your tool is probably VIRT + RES + SHR, which in my case would be 4GB+) while in reality it is 132MB.