We have looked into your issue. To change the ram size of the AVD follow below steps.

1. Open android studio. 

2. Click on tools menu ---> android ---> SDK manager. It will open list of AVD's

3. Select specific AVD which you want to edit --> a new window will open. In this window at below you will find one option "Show Advanced Setting", click on it. Scroll down you will find RAM option. Edit it to 900 MB.

4. Click on Finish.

Hope above steps will resolve your issue. Please let us know if still any issue persist. We would be happy to assist you.