DeviceCapacity and AvailableDeviceCapacity in DeviceInformation command sent from the device to MDM is different from the capacity shown in devices settings 'About' page

Other EMM Platforms
1

The Device Information Queried from the device using MDM. The values for DeviceCapacity (Floating-point gigabytes (base-1024 gigabytes) ) and AvailableDeviceCapacity (Floating-point gigabytes (base-1024 gigabytes)) is not the same as in the device Settings --> General --> About page.

Observed in all recent iOS versions in all iOS model devices.

Response for DeviceInformation command sent to device from MDM

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>CommandUUID</key>
	<string>Enrollment</string>
	<key>QueryResponses</key>
	<dict>
		<key>AvailableDeviceCapacity</key>
		<real>166.148193359375</real>
                <key>DeviceCapacity</key>
		<real>230.2630615234375</real>
		<key>IsSupervised</key>
		<true/>
		<key>Model</key>
		<string>MQ8G2HN</string>
		<key>ModelName</key>
		<string>iPhone</string>
		<key>OSVersion</key>
		<string>12.1.4</string>
		<key>ProductName</key>
		<string>iPhone10,2</string>
	</dict>
	<key>Status</key>
	<string>Acknowledged</string>
	<key>UDID</key>
	<string>3*************5</string>
</dict>
</plist>

But in the device About
The capacity is 256GB and Available is 190.89 GB

Any idea on why such discrepancy exist?

2

This doesn’t explain all the discrepancy but the iPhone storage is calculated same as hard drive storage

1GB = 1 billion bytes, and 1TB = 1 trillion bytes; actual formatted capacity less.

i.e. 256GB = 256000000000 bytes which is in reality around 238.42 GB

3

I had thought the same, but still leaves a ~20Gb discrepancy.

@Annbarasi Can you share details on the MDM you are using? (including version)