You can share the license across the multiple devices. So if you want use the app on both tablet and phone, you do NOT need to purchase the multiple license.
The license sharing is only available for the auto-renewal subscription license. The fixed term license can not be shared.
How to retreive the license information.
Setting > License > License Tools > Restore button
Setting > License > Restore button
The license information is tied with your Google or iTunes account. So,,,
For Android, you must login to the deice with the same Google account as you purchased the license.
For iOS, you must log into iTunes store with the same iTunes account as you purchased the license.