Settlement times and delays are specified on your platform's spec sheet and refer to the amount of time it takes Synapse to batch out a transaction.
Once Synapse has batched out a transaction it will receive a trace ID (A unique number assigned to every ACH entry by an Originating Depository Financial Institution which identifies that entry within a specific ACH file. The first 8 digits of the trace number are the transit/routing number of the ODFI and the last 7 digits are sequence numbers assigned by the originator.)
Once Synapse receives a batch file from the receiving depository financial institution (RDFI) we can then mark the transaction as settled.
See RDC (Remote Deposit Capture) Settlement Times for an example of how this logic applies to a specific transaction type.