Each transaction is hashed using SHA-256 resulting in a unique ID for the transaction.  A single transaction can have multiple outputs, each with their own "Value:" and "scriptPubKey:".  The "Previous Tx:" is the hash value indicating which previous transaction contains the output that is being spent, but you still need to identify which of the potentially many outputs in that transaction is the one being spent.  The "Index:" indicates which of the outputs from the previous transaction are being used as the input of the current transaction. It references the entire output, not just the value.