Similar to what happens in Monzo with Pots transactions, Starling also provides their users with internal savings areas, which they call "Spaces" or Goals. You can find more information here.
If you wish to filter those transactions, use the provider_source field returned in meta. The value INTERNAL_TRANSFER indicates transactions to and from Spaces.
Example:
"meta": {
"provider_transaction_id": "6cf2855a-67c6-4931-ad96-a46980341333",
"provider_source": "INTERNAL_TRANSFER"
}
Please note: The meta object in the /transactions response is a collection of additional provider specific transaction metadata - it may not always be returned by the provider.