Wait a moment… I think we are dealing with 2 things at the time.

If you want to see how much memory your APIM has, you need to create an interrogator USB from the Utilities tab in the app. THIS DOES NOT UPDATE/MODIFY YOUR APIM, it just extracts information. Since the interrogator is based of your current Sync version, that’s why avdonr said you need to confirm and configure your current version in the app first.

Again, you do not create an update package at the moment, just the interrogator one.

More about the interrogator → https://cyanlabs.net/docs/syn3updater/page/create-interrogator-log-usb

You will find other documentation there.