The scaled mode uses a toggle keyboard shortcut Host Key + સી. By default the Host Key in VirtualBox is the right Ctrl key પર Linux અને વિન્ડોઝ. On Mac it is the left Command Key. If you have changed your Host key you can check it by going to File -> Preferences -> Input -> Virtual Machine -> Host Key Combination .
If you are in scaled mode pressing the Host Key + સી will exit scaled mode.