Can't Use 2G RAM

What I expected to happen was...:
To Play With 2G of Ram Used

What actually happened was...:
It Crashed on 2G Ram, ONLY 2G though

Steps to Reproduce:
1. Open Minecraft
2. Go To Edit Profile
3. Go To JVX Java Arguments
4. Check The Box
5. Replace 1G with 2G
6. Watch It Crash