Once you are done with your test session, you need to release the device to save your credits. 

To release a device click on the red Release button at the top right corner.

A pop up will appear confirming to clean up your device. Click on 'yes' to clean up and release a device.

Device Cleanup

Remove all applications installed on the device during a session. The cleanup behaves differently on public and dedicated clouds.

Cleanup in public cloud
As the devices are shared, the cleanup is performed automatically when a device is closed for security purposes.

However, public cloud users should always clean a device and remove any personal data before returning the device to the device pool. This includes, but is not limited to, email accounts, browser cookies/open tabs, and any manually configured WiFi VPN settings.

Cleanup in dedicated clouds
Cleanup is not performed automatically, when a device is closed; a popup appears that prompts the user to perform cleanup.